We are already three weeks into a new semester. And our GPS Group also meet for the first time last week. (For us, the “G” stands for Goal, not Global.) We share about our goals for the semester. Getting good grades, completing projects, that sort of thing. But a student also shares how he wants to take some subjects outside his major, learn some new things, and make some new friends.
Then we discuss how some goals are only short term. If we get good grades this term, we are happy for a moment; then we have to start again for the next term. The achievements last term mean very little if we don’t get good grades this term. In addition to these short term goals, we also need to know what our long term goals are. Otherwise it is possible to achieve our short term goals, but ultimately failing to achieve our long term goals. For example, if our long term goal is to be a scientist, then we have to ask whether we are studying the right program, the right subjects, or even studying the right way.
We often see some students getting good grades because they are good at taking examinations, not necessarily because they have a good grasp of the subject of study. On the other hand, there are students who are good in programming or solving problems but failing to get the best grades because they are not very good at taking examinations. In the long run, who is going to be more successful?
It is a bit like the encounter between Jesus and the Samaritan woman. He was thirsty and asked the woman for water. Later he took the occasion to tell the woman that people who drink water will be thirsty again. But He can give living water which brings eternal life.
It is obvious that it is the long term goals that are more important. We did not have a lot of time, but the students showed keen interest. There were a lot of interesting questions and thoughts expressed. We had a good start to the semester.
[The building is not on fire. It is just a reflection of the setting sun. But appearances can be deceiving sometimes.]
Sunday, January 31, 2010
Saturday, January 30, 2010
Insurance
When the old building came crashing down, one of the issues that came up was insurance and compensation.
Nowadays we try to insure against more and more things: damage or theft of your car, bodily injury or property damage to others caused by your car, damage or destruction to your home due to disasters, such as fire, flood, or earthquakes, medical insurance, dental insurance, disability insurance, worker’s compensation, crime insurance, political risk insurance, life insurance, mortgage insurance, property insurance, collatoral protection insurance, kidnap and ransom insurance, pet insurance, ...
How many and how much of these do you have?
There are reasons to purchase any and all of these insurances, some more reasonable than others. The basic reason is, I suppose, to protect myself or loved ones against the possibility of bad things happening. But I have a strong aversion to buying many types of insurance.
Perhaps I am just cheap, lazy, overly optimistic, or downright irresponsible. But I do have philosophical and practical objections. To provide for the amount of insurance that really makes an impact, the premium that I have to pay is just way too much. If the amount of insurance is not really sufficient, then what is the point of buying the insurance?
More importantly, it is better to put the effort into living a full and meaningful life. Rather than to spend our time and effort protecting against all kinds of disasters and mishaps - which are just too numerous to even contemplate.
Nowadays we try to insure against more and more things: damage or theft of your car, bodily injury or property damage to others caused by your car, damage or destruction to your home due to disasters, such as fire, flood, or earthquakes, medical insurance, dental insurance, disability insurance, worker’s compensation, crime insurance, political risk insurance, life insurance, mortgage insurance, property insurance, collatoral protection insurance, kidnap and ransom insurance, pet insurance, ...
How many and how much of these do you have?
There are reasons to purchase any and all of these insurances, some more reasonable than others. The basic reason is, I suppose, to protect myself or loved ones against the possibility of bad things happening. But I have a strong aversion to buying many types of insurance.
Perhaps I am just cheap, lazy, overly optimistic, or downright irresponsible. But I do have philosophical and practical objections. To provide for the amount of insurance that really makes an impact, the premium that I have to pay is just way too much. If the amount of insurance is not really sufficient, then what is the point of buying the insurance?
More importantly, it is better to put the effort into living a full and meaningful life. Rather than to spend our time and effort protecting against all kinds of disasters and mishaps - which are just too numerous to even contemplate.
Collapse
An old building in Hung Hom collapsed suddenly this afternoon. It is not far from where I live. And very close to where my wife lived as a child. Those of us who live in Hong Kong have probably seen and heard a lot about it. Here are some photographs for my friends overseas.
This is the south end of the section of street, looking north. The collapsed building is of the same type and age of the buildings on the right (east) side of the street. They are about 55 years old. 18 buildings in a row. The collapsed building is the last one at the north.
Some heavy equipment is being used in excavation. Three persons have been found dead so far. Two are still missing.
This is the north end of that section of street. The collapsed building should have been standing behind the yellow dump truck.
The collapse ripped gaping holes in the building next to it. The collapsed building shared a staircase with the next building. The staircase has collapsed with the building, leaving the next building without access, and in grave danger of falling down as well. The residents have been evacuated. Many of them through the windows by firemen.
The top flight of stairs is still attached to the next building, hanging in mid-air. Some said the collapse was caused by the damage done to the building by the removal of unauthorized additions to the collapsed building in the past 2 days. Others blame construction work near the foundations of the collapsed building. The truth has yet to be determined.
The whole thing is very scary.
This is the south end of the section of street, looking north. The collapsed building is of the same type and age of the buildings on the right (east) side of the street. They are about 55 years old. 18 buildings in a row. The collapsed building is the last one at the north.
Some heavy equipment is being used in excavation. Three persons have been found dead so far. Two are still missing.
This is the north end of that section of street. The collapsed building should have been standing behind the yellow dump truck.
The collapse ripped gaping holes in the building next to it. The collapsed building shared a staircase with the next building. The staircase has collapsed with the building, leaving the next building without access, and in grave danger of falling down as well. The residents have been evacuated. Many of them through the windows by firemen.
The top flight of stairs is still attached to the next building, hanging in mid-air. Some said the collapse was caused by the damage done to the building by the removal of unauthorized additions to the collapsed building in the past 2 days. Others blame construction work near the foundations of the collapsed building. The truth has yet to be determined.
The whole thing is very scary.
Wednesday, January 27, 2010
No money? No justice.
Now what a lot of us were afraid of has really happened. Three small investors were forced to give up suing a tycoon because they did not have the money to continue.
In 2008 the big conglomerate CITIC Pacific lost a hugh amount of money because of bets on the Australian dollar. Its stock slumped 55% in one day. Many people who thought its was a well-run company lost big.
Three small investors sued the CITIC Pacific boss in the Small Claims Court, where the claims are for less than $50,000 and lawyers are not allowed. They claimed that the boss made false and misleading statements even when the losses were taking place, leading them to invest in the company while unaware of the company’s blood-letting.
The (former) boss asked for the case to be moved to the High Court, claiming that the case was too complex to be investigated by the Small Claims Court. The Small Claims Court has now agreed. The three small investors don’t have the money for the legal fees necessary to pursue the lawsuit in the High Court. They are forced to give up.
Everything sounds so logical. But the stark reality is: if you don’t have the money, rich people can step over you (perhaps they did not mean to, you just happen to be in the way), and you cannot even complain. That is justice, Hong Kong style.
In 2008 the big conglomerate CITIC Pacific lost a hugh amount of money because of bets on the Australian dollar. Its stock slumped 55% in one day. Many people who thought its was a well-run company lost big.
Three small investors sued the CITIC Pacific boss in the Small Claims Court, where the claims are for less than $50,000 and lawyers are not allowed. They claimed that the boss made false and misleading statements even when the losses were taking place, leading them to invest in the company while unaware of the company’s blood-letting.
The (former) boss asked for the case to be moved to the High Court, claiming that the case was too complex to be investigated by the Small Claims Court. The Small Claims Court has now agreed. The three small investors don’t have the money for the legal fees necessary to pursue the lawsuit in the High Court. They are forced to give up.
Everything sounds so logical. But the stark reality is: if you don’t have the money, rich people can step over you (perhaps they did not mean to, you just happen to be in the way), and you cannot even complain. That is justice, Hong Kong style.
Tuesday, January 26, 2010
由儉入奢易
Chris’ comment on the previous post on Salted Garoupas reminded me of the saying 由儉入奢易,由奢入儉難。
I lived for many years in upstate New York where it was quite difficult to get good seafood as we know them in Hong Kong. Later I moved to Toronto and then Ottawa. There were more fish available. But mostly fresh water fish, which are nowhere nearly as good as live ocean catch.
When I moved back to Hong Kong, I found myself in seafood heaven. There is so much to choose from. Not just live garoupas, but also ocean prawns, Pacific lobsters, Atlantic lobsters, giant mantis shrimps, geoducks, ocean crabs, fresh water crabs, scallops, giant clams, squids, cuttle fish, eels, abalone, ... It will be hard, if and when I have to move away from Hong Kong again.
It is certainly easy to go from eating frozen, bland fish fillets to eating live, ocean-caught garoupas. But it is much harder handling going the other way around.
In the same way, she who can handle adversity - particularly if she started out rich - is demonstrably strong. But he who has always been rich cannot be said to be strong - he has not been tested yet.
I lived for many years in upstate New York where it was quite difficult to get good seafood as we know them in Hong Kong. Later I moved to Toronto and then Ottawa. There were more fish available. But mostly fresh water fish, which are nowhere nearly as good as live ocean catch.
When I moved back to Hong Kong, I found myself in seafood heaven. There is so much to choose from. Not just live garoupas, but also ocean prawns, Pacific lobsters, Atlantic lobsters, giant mantis shrimps, geoducks, ocean crabs, fresh water crabs, scallops, giant clams, squids, cuttle fish, eels, abalone, ... It will be hard, if and when I have to move away from Hong Kong again.
It is certainly easy to go from eating frozen, bland fish fillets to eating live, ocean-caught garoupas. But it is much harder handling going the other way around.
In the same way, she who can handle adversity - particularly if she started out rich - is demonstrably strong. But he who has always been rich cannot be said to be strong - he has not been tested yet.
Monday, January 25, 2010
老鼠斑鹹魚
Sunday, January 24, 2010
Love United Hate Glazer
My favourite sports team, Manchester United, won a soccer game by 4 to 0. Wayne Rooney, scored all 4 goals. I have been following them since the late 1960s, in the days of Dennis Law, George Best and Bobby Charlton. In those days I had a notebook in which I wrote down all the scores and analyzed the data by hand. Later in university, I wrote a program in Pascal to store the results. I did not have access to a database at the time, and had to create a format to achieve the data in a file.
All the fans, including myself, are of course very happy that United won in such a fashion.
However, all these achievements were overshadowed by the owners’ continued and escalating shenanigans. That is why may of the fans were wearing buttons with the slogan “Love United Hate Glazers”. The Glazers are the wealthy Americans who bought the team in 2005. They are not soccer fans. But they borrowed a huge amount of money in order to purchase the team, and a large chunk of the debt somehow became the team’s debt. The interest alone amounts to 100 million US dollars a year and is of course rising every minute.
Doesn’t it sound familiar to us? Isn’t it the same old story as what happened in Hong Kong when some rich tycoon took over a big, stable and healthy telecommunication company? And in the process crippled in with a humongous amount of debt?
The worst is still coming at Manchester United. Since the take over, ticket prices have risen. Great players such as Christiano Ronaldo has been sold for huge amounts of money. Less and less money is available for buying new players. The money earned from the tickets is not enough even to make the interest payments.
Now the Glazers are refinancing again, putting more debt on Manchester United. While they take cash from the team for themselves. I hate to think of the day when they have to sell Wayne Rooney.
Isn’t it disgusting? Can you blame the fans for saying “Love United Hate Glazers”?
All the fans, including myself, are of course very happy that United won in such a fashion.
However, all these achievements were overshadowed by the owners’ continued and escalating shenanigans. That is why may of the fans were wearing buttons with the slogan “Love United Hate Glazers”. The Glazers are the wealthy Americans who bought the team in 2005. They are not soccer fans. But they borrowed a huge amount of money in order to purchase the team, and a large chunk of the debt somehow became the team’s debt. The interest alone amounts to 100 million US dollars a year and is of course rising every minute.
Doesn’t it sound familiar to us? Isn’t it the same old story as what happened in Hong Kong when some rich tycoon took over a big, stable and healthy telecommunication company? And in the process crippled in with a humongous amount of debt?
The worst is still coming at Manchester United. Since the take over, ticket prices have risen. Great players such as Christiano Ronaldo has been sold for huge amounts of money. Less and less money is available for buying new players. The money earned from the tickets is not enough even to make the interest payments.
Now the Glazers are refinancing again, putting more debt on Manchester United. While they take cash from the team for themselves. I hate to think of the day when they have to sell Wayne Rooney.
Isn’t it disgusting? Can you blame the fans for saying “Love United Hate Glazers”?
Saturday, January 23, 2010
Violent protesters?
Some of the university students who were there protesting outside the Legislative Council last Saturday (16 January) are very indignant. They said they have only been peacefully singing, discussing, and making speeches most of the time. Many of them are first time protesters. The worst that they did, and only for brief periods, was to block the exits and to push against the barriers, in an effort to speak to the government officials and the legislators.
Now they are being accused of being violent, and seriously disturbing the order of the community.
Perhaps the government officials and some of the legislators from functional constituencies were really scared. A video of them (about 10 to 15) fleeing from the MTR was posted on the Internet. They could be seen to be protected by a thick layer of more than 70 police officers, as if they are under threat of serious harm. Yet no pursurers of any kind can be seen in the video. It looks more like a bit of paranoia.
What is better? For the young people to be apathetic? Or to care enough about a costly railway project that wil have a big impact on society, to stage a sit-in?
Yet the government keeps stonewalling, refusing to speak with the young people, and refusing to give the citizens a reasonable period of time to address many of the concerns raised. Perferring to rely on the many legislators “elected” from very small closed circles masquerading as functional constituencies, to push through a very costly project that is bound to further enrich many of the wealthiest in the community.
“Elected” legislators are refusing to speak to the people they are supposed to represent. Government officials are refusing to speak to the people they are supposed to serve.
Now the government is trying to paint the few perhaps a bit agitated young people as violent mobsters. Most of us do not condone violence, and prefer to see the protesters refrain from even pushing and shoving. But can we really blame the people for being upset? The government must bear a large part of the responsibilities for causing this to happen.
Now they are being accused of being violent, and seriously disturbing the order of the community.
Perhaps the government officials and some of the legislators from functional constituencies were really scared. A video of them (about 10 to 15) fleeing from the MTR was posted on the Internet. They could be seen to be protected by a thick layer of more than 70 police officers, as if they are under threat of serious harm. Yet no pursurers of any kind can be seen in the video. It looks more like a bit of paranoia.
What is better? For the young people to be apathetic? Or to care enough about a costly railway project that wil have a big impact on society, to stage a sit-in?
Yet the government keeps stonewalling, refusing to speak with the young people, and refusing to give the citizens a reasonable period of time to address many of the concerns raised. Perferring to rely on the many legislators “elected” from very small closed circles masquerading as functional constituencies, to push through a very costly project that is bound to further enrich many of the wealthiest in the community.
“Elected” legislators are refusing to speak to the people they are supposed to represent. Government officials are refusing to speak to the people they are supposed to serve.
Now the government is trying to paint the few perhaps a bit agitated young people as violent mobsters. Most of us do not condone violence, and prefer to see the protesters refrain from even pushing and shoving. But can we really blame the people for being upset? The government must bear a large part of the responsibilities for causing this to happen.
Friday, January 22, 2010
Chivalry
It was early in the morning. A man was paying for something at the counter at the convenience store. I grabbed a newspaper, stood behind him, slightly to his right, and waited.
A young man appeared to his left and put down two buns, wrapped in plastic, on the counter. He was getting ready to pay for the buns.
Should I plunk down my newspaper, to remind the young man that I was there before him? He probably did not see me. It wouldn’t take him too long to pay. It is just a delay of seconds. OK, I will just let him go ahead and not make a fuss.
Suddenly, the young man picked up the buns, and smiled at me. Evidently he saw me, realized that I was there before him, and decided to let me pay first.
I liked him instantly, and smiled back at him. My day started brightly.
A young man appeared to his left and put down two buns, wrapped in plastic, on the counter. He was getting ready to pay for the buns.
Should I plunk down my newspaper, to remind the young man that I was there before him? He probably did not see me. It wouldn’t take him too long to pay. It is just a delay of seconds. OK, I will just let him go ahead and not make a fuss.
Suddenly, the young man picked up the buns, and smiled at me. Evidently he saw me, realized that I was there before him, and decided to let me pay first.
I liked him instantly, and smiled back at him. My day started brightly.
Thursday, January 21, 2010
Was OJ the killer?
In 1994, Nicole Brown Simpson was found murdered, together with a male companion. Her ex-husband, the famous footballer O. J. Simpson, was suspected to have committed the murder.
His defense lawyer, the famous lawyer Derschowitz reasoned this way: 4 million women are battered each year by husbands and boyfriends in the USA. Yet in 1992, only 1,432, or 1 in 2,500, were killed by their husbands and boyfriends. Hence few men who slap or beat their domestic partners go on to murder them. In the end, O. J. Simpson was found not guilty. [statistics A]
However, of all the battered women murdered in the USA in 1993, 90 percent were killed by the abuser. [statistics B]
I read about the O. J. Simpson case and statistics A a long time ago. But I read statistics B in The Drunkard’s Walk only recently.
The probability that a abusing man will kill the abused woman (not too high) and the probability that a murdered woman is killed by the abusing man (almost a certainty) are vastly different things. Sadly, people often confuse the two.
His defense lawyer, the famous lawyer Derschowitz reasoned this way: 4 million women are battered each year by husbands and boyfriends in the USA. Yet in 1992, only 1,432, or 1 in 2,500, were killed by their husbands and boyfriends. Hence few men who slap or beat their domestic partners go on to murder them. In the end, O. J. Simpson was found not guilty. [statistics A]
However, of all the battered women murdered in the USA in 1993, 90 percent were killed by the abuser. [statistics B]
I read about the O. J. Simpson case and statistics A a long time ago. But I read statistics B in The Drunkard’s Walk only recently.
The probability that a abusing man will kill the abused woman (not too high) and the probability that a murdered woman is killed by the abusing man (almost a certainty) are vastly different things. Sadly, people often confuse the two.
Tuesday, January 19, 2010
Community Service-Learning Program (CSLP) Awards
Today, our students’ work in service learning was recognized by our university by two awards. The Gold Award (first prize) in CSLP for the Gansu orphan school project, and the Bronze Award (third prize) for the Refugee Children project. The Hong Chi Special School project also received a Merit Award.
We have many more students involved in these projects. And several more projects besides these three. Some of the students were at classes, and others were at work at their placement companies; so they could not come to the ceremony. This year alone, we probably have 40 to 50 students involved in a variety of projects. We are really proud of our students. They serve a lot of needy people, make use of what they learn in university, make a lot of friends, and learn a lot from the experience. We, as their advisors, work hard too, to set up these projects and to work alongside them. But it is worth it.
We have many more students involved in these projects. And several more projects besides these three. Some of the students were at classes, and others were at work at their placement companies; so they could not come to the ceremony. This year alone, we probably have 40 to 50 students involved in a variety of projects. We are really proud of our students. They serve a lot of needy people, make use of what they learn in university, make a lot of friends, and learn a lot from the experience. We, as their advisors, work hard too, to set up these projects and to work alongside them. But it is worth it.
Sunday, January 17, 2010
Ship Street Haunted House - in 2009
On a less serious topic - my wife and I went to the haunted house at the end of Ship Street in Wanchai at the end of the last decade. It may sound like a long time, but it was actually less than a month ago.
The last time I was there, probably two years ago, I was able to go up to the front gate at the top of the stairs and peeked inside the courtyard. It was a sunny day. But I was alone, the whole place was deserted, it was shaded by big trees, it felt unusually cool, and slightly dark, ..., it was a little spooky. of course, it was all just in my mind. Nothing actually happened.
But this time, unfortunately, the stairs leading up to the house was already blocked up. We could only look at it from a distance. It may not look scary from such a distance, but this is arguably the most famous haunted house in Hong Kong. Many stories have been told. I do have more photographs of the place in my previous post.
Sadly, like most things in Hong Kong with a history, whether famous or infamous, it is unlikely to last very long.
The last time I was there, probably two years ago, I was able to go up to the front gate at the top of the stairs and peeked inside the courtyard. It was a sunny day. But I was alone, the whole place was deserted, it was shaded by big trees, it felt unusually cool, and slightly dark, ..., it was a little spooky. of course, it was all just in my mind. Nothing actually happened.
But this time, unfortunately, the stairs leading up to the house was already blocked up. We could only look at it from a distance. It may not look scary from such a distance, but this is arguably the most famous haunted house in Hong Kong. Many stories have been told. I do have more photographs of the place in my previous post.
Sadly, like most things in Hong Kong with a history, whether famous or infamous, it is unlikely to last very long.
Saturday, January 16, 2010
Busy Saturday - Service-Learning
In the morning, we have a group of primary school students coming to the department to learn to build and program robots from our students.
At the same time, we have a group of refugee claimants (from Africa and South Asia) coming in to learn how to put together a computer from our students.
In the afternoon, we have another group of seniors coming in to learn flash animation from our students.
These are all part of our Community Outreach Merit Program (COMP), i.e., service learning - our university students learning through community service. I am very proud of our students and the staff who work so hard to put these programs together.
At the same time, we have a group of refugee claimants (from Africa and South Asia) coming in to learn how to put together a computer from our students.
In the afternoon, we have another group of seniors coming in to learn flash animation from our students.
These are all part of our Community Outreach Merit Program (COMP), i.e., service learning - our university students learning through community service. I am very proud of our students and the staff who work so hard to put these programs together.
Wednesday, January 13, 2010
Release LIU Xiaobo - 釋放劉曉波燭光晚會
There was a Candle Light Vigil outside the Legislative Council this evening (12 Jan 2010), to press for the release of LIU Xiaobo. There appeared to be several hundred people there. I thought there would be more. However, I felt encouraged that there were at least quite a number of people who felt strongly enough to come. It was cold, about 10 degrees Celsius. But it did not feel cold.
There were some familiar faces. There were also quite a few non-Chinese, who probably did not understand much of what was said, because most of the speakers spoke in Chinese. But they stayed. Evidently they understood enough and felt strongly enough about the quest for justice and democracy to stay and show their support. There were some people from mainland China.
Some people talked about the LIU Xiaobo that they know, some talked about his wife and how she stood by him, some read aloud his writings, some sang songs composed for him, ... The message was very clear: He should not be punished just for speaking out, asking for openness and democracy.
There were, as usual, a lot of police who stood watch. At least, they did not look too tense.
There were some familiar faces. There were also quite a few non-Chinese, who probably did not understand much of what was said, because most of the speakers spoke in Chinese. But they stayed. Evidently they understood enough and felt strongly enough about the quest for justice and democracy to stay and show their support. There were some people from mainland China.
Some people talked about the LIU Xiaobo that they know, some talked about his wife and how she stood by him, some read aloud his writings, some sang songs composed for him, ... The message was very clear: He should not be punished just for speaking out, asking for openness and democracy.
There were, as usual, a lot of police who stood watch. At least, they did not look too tense.
Sunday, January 10, 2010
HIV tests and HIV
The HIV test produced a positive result when the blood was not infected with the AIDS virus (false positive) in only 1 in 1,000 blood samples. So the doctor concluded Mlodinow has a 1 in 1,000 chance of being healthy, when his test came out positive.
The problem is, his doctor confused two things:
(1) the chance that Mlodinow would test positive if he was not HIV-positive, with
(2) the chances that he would not be HIV-positive if he tested positive.
The first was indeed 1 in 1,000.
But to determine the second, more information is needed. Mlodinow is white, heterosexual, and does not abuse drugs. According to statistics from the Centers for Disease Control and Prevention, about 1 in 10,000 heterosexual non-IV-drug-abusing white male Americans who got tested were infected with HIV.
Consider a population of 10,000 such people. About 1 in the 10,000 was actually infected with HIV. Assume that the false-negative rate (infected by HIV but the test came out negative) is near 0. That means about 1 person from the population will test positive due to presence of the infection (true positive). Since the rate of false positives is 1 in 1,000, there will be 10 others who are not infected with HIV but test positive anyway (false positive). The other 9,989 will test negative (true negative).
So there are 10 false positives and 1 true positive. Only 1 out of the 11 who test positive are really infected with HIV. The answer to the second question is 10 out of 11. Not 1 out of 1,000. There is a big difference. Some basic understanding of probability is really quite useful, both in daily life, and as a professional.
This case was in The Drunkard's Walk. It is really a fascinating and useful book.
The problem is, his doctor confused two things:
(1) the chance that Mlodinow would test positive if he was not HIV-positive, with
(2) the chances that he would not be HIV-positive if he tested positive.
The first was indeed 1 in 1,000.
But to determine the second, more information is needed. Mlodinow is white, heterosexual, and does not abuse drugs. According to statistics from the Centers for Disease Control and Prevention, about 1 in 10,000 heterosexual non-IV-drug-abusing white male Americans who got tested were infected with HIV.
Consider a population of 10,000 such people. About 1 in the 10,000 was actually infected with HIV. Assume that the false-negative rate (infected by HIV but the test came out negative) is near 0. That means about 1 person from the population will test positive due to presence of the infection (true positive). Since the rate of false positives is 1 in 1,000, there will be 10 others who are not infected with HIV but test positive anyway (false positive). The other 9,989 will test negative (true negative).
So there are 10 false positives and 1 true positive. Only 1 out of the 11 who test positive are really infected with HIV. The answer to the second question is 10 out of 11. Not 1 out of 1,000. There is a big difference. Some basic understanding of probability is really quite useful, both in daily life, and as a professional.
This case was in The Drunkard's Walk. It is really a fascinating and useful book.
Friday, January 08, 2010
Drunkard’s Walk
Mlodinow’s doctor told him chances are 999 out of 1,000 that he’d be dead within 10 years. That was because Mlodinow’s HIV test came back positive.
The HIV test produced a positive result when the blood was not infected with the AIDS virus (false positive) in only 1 in 1,000 blood samples. So the doctor concluded Mlodinow has a 1 in 1,000 chance of being healthy.
Was Mlodinow’s doctor correct?
The following information may be useful. Mlodinow is white, heterosexual, and does not abuse drugs. According to statistics from the Centers for Disease Control and Prevention, about 1 in 10,000 heterosexual non-IV-drug-abusing white male Americans who got tested were infected with HIV.
The HIV test produced a positive result when the blood was not infected with the AIDS virus (false positive) in only 1 in 1,000 blood samples. So the doctor concluded Mlodinow has a 1 in 1,000 chance of being healthy.
Was Mlodinow’s doctor correct?
The following information may be useful. Mlodinow is white, heterosexual, and does not abuse drugs. According to statistics from the Centers for Disease Control and Prevention, about 1 in 10,000 heterosexual non-IV-drug-abusing white male Americans who got tested were infected with HIV.
Thursday, January 07, 2010
“Best” Students in Hong Kong
I met a student today from one of the elite secondary schools in Hong Kong. At one point the conversation turned to examinations. He had 9 As from the Hong Kong Certificate of Education Examinations (HKCEE). Not from this year. So don’t bother to identify him or the school.
I know many students prepare for the HKCEE by working on past examination papers. So I asked him about it. He said, “I did not do that many.” I pressed him on it, “How many is not too much?”
He: “I only worked on papers for the last 10 years.” When he saw my surprise at his referring to 10 years as not too many, he explained, “It is really not that many. Some of my classmates went through the papers for the last 20 years.”
I am not so naive to be surprised that students rely so much on studying past examination papers. I am just surprised that 10 years is now considered “not too many.”
I know many students prepare for the HKCEE by working on past examination papers. So I asked him about it. He said, “I did not do that many.” I pressed him on it, “How many is not too much?”
He: “I only worked on papers for the last 10 years.” When he saw my surprise at his referring to 10 years as not too many, he explained, “It is really not that many. Some of my classmates went through the papers for the last 20 years.”
I am not so naive to be surprised that students rely so much on studying past examination papers. I am just surprised that 10 years is now considered “not too many.”
Wednesday, January 06, 2010
Where is the car? (answer)
There are 3 possible outcomes, each having the probability of 1/3. Your chances of having guessed right, when you chose one of the doors, is 1/3. No mysteries here.
The probability of you having guessed wrong is 2/3. In this scenerio, owning to the action of the host (opening the door with a goat), you will win if you switch. So it is better to switch. In fact, you double your chances of winning by switching.
Statistics from the actual television show in which this game appeared bear this out. Those who found themselves in this situation and switched their choices won about twice as often as those who did not. Computer simulations also reached the same conclusion. By the way, this problem is sometimes referred to as the Monty Hall problem. You can Google it for more detailed analysis.
The Drunkard’s Walk has many of these fascinating examples of use (and misuse) of probability. Highly recommended.
The probability of you having guessed wrong is 2/3. In this scenerio, owning to the action of the host (opening the door with a goat), you will win if you switch. So it is better to switch. In fact, you double your chances of winning by switching.
Statistics from the actual television show in which this game appeared bear this out. Those who found themselves in this situation and switched their choices won about twice as often as those who did not. Computer simulations also reached the same conclusion. By the way, this problem is sometimes referred to as the Monty Hall problem. You can Google it for more detailed analysis.
The Drunkard’s Walk has many of these fascinating examples of use (and misuse) of probability. Highly recommended.
Tuesday, January 05, 2010
Where is the car?
You are in a game show where there are three doors. Behind one door is a car; behind the other doors, goats. After you pick a door, the host, who knows what is behind all the doors, opens one of the unchosen doors, which reveals a goat. He then asks you, “Do you want to switch to the other unopened door?” Is it to your advantage to make the switch?
A lot of people, including many PhDs and mathematics professors, say it is evident that whether you change your choice or not, your chances of winning are 50/50.
But Leonard Mlodinow says in his book “The Drunkard’s Walk” it is better to switch. Do you agree? Actually Mlodinow was citing Marilyn vos Savant, a fascinating person herself.
I will post the answer tomorrow. In the mean time, feel free to read Mlodinow’s book. It is a fascinating introduction to probability. He makes a dry and difficult subject fun. People who are teaching probability may find some useful cases there.
A lot of people, including many PhDs and mathematics professors, say it is evident that whether you change your choice or not, your chances of winning are 50/50.
But Leonard Mlodinow says in his book “The Drunkard’s Walk” it is better to switch. Do you agree? Actually Mlodinow was citing Marilyn vos Savant, a fascinating person herself.
I will post the answer tomorrow. In the mean time, feel free to read Mlodinow’s book. It is a fascinating introduction to probability. He makes a dry and difficult subject fun. People who are teaching probability may find some useful cases there.
Monday, January 04, 2010
New Year March for Democracy (2)
Having started the march in the middle of the procession, I gradually moved towards the front simply because I want to see who were marching. About half way through, I found myself at the very front, right next to the leaders, and behind the truck that opened the road ahead for the marchers.
All the time, the march was peaceful and orderly. Towards the end, the police presence was getting heavier and heavier. They did not look particularly tense, however.
At the destination, we were across the road from the Liaison Office. I watched the leaders mount the stage, which was so small that some of them were in danger of falling off. There was no real gathering space. It consisted of the sidewalk outside of Western Police Station and one lane of the 4 lane Des Voeux Road. It was obvious the police were doing all it can to make it inconvenient for the marchers. But the people seemed relaxed. Some were smiling. There was little tension.
I stuck around the neighbourhood for half and hour, watching the rest of the marchers arrived and dispersed. Everything was orderly. Several demands were prominent: fair elections, abolishment of functional constituencies, and freedom for Liu Xiao Bo.
The commotion caused by people who rushed the Liason Office happened long after I left. I want to voice my opinion and demands peacefully. I do not agree with violence. I may not participate in such marches in the future. I am afraid people who employed radical, even violent means are hurting the peaceful movement towards fair elections and democracy.
On the other hand, the government, the people in power, and the police are not showing the respect and willingness to listen to the demands of the people. If they persist in stonewalling, some people in society may resort to more radical and violent means to press for their demands. They cannot wash their hands of the responsibility should that happens.
All the time, the march was peaceful and orderly. Towards the end, the police presence was getting heavier and heavier. They did not look particularly tense, however.
At the destination, we were across the road from the Liaison Office. I watched the leaders mount the stage, which was so small that some of them were in danger of falling off. There was no real gathering space. It consisted of the sidewalk outside of Western Police Station and one lane of the 4 lane Des Voeux Road. It was obvious the police were doing all it can to make it inconvenient for the marchers. But the people seemed relaxed. Some were smiling. There was little tension.
I stuck around the neighbourhood for half and hour, watching the rest of the marchers arrived and dispersed. Everything was orderly. Several demands were prominent: fair elections, abolishment of functional constituencies, and freedom for Liu Xiao Bo.
The commotion caused by people who rushed the Liason Office happened long after I left. I want to voice my opinion and demands peacefully. I do not agree with violence. I may not participate in such marches in the future. I am afraid people who employed radical, even violent means are hurting the peaceful movement towards fair elections and democracy.
On the other hand, the government, the people in power, and the police are not showing the respect and willingness to listen to the demands of the people. If they persist in stonewalling, some people in society may resort to more radical and violent means to press for their demands. They cannot wash their hands of the responsibility should that happens.
Friday, January 01, 2010
New Year March for Democracy 爭取普選元旦遊行
I was not planning to go to the march today. I support democracy and fair elections, of course. But I am not so sure about the strategies that some of the politicians are advocating. But then Liu Xiao Bo was sentenced to 10 years in prison, just for peacefully advocating democracy. That is very upsetting. So I decided this morning to join up.
When I got out of the MTR at Charter Street, I found myself stuck in the middle of the crowd. I estimated the crowd to be about 10,000. It was not scientific, of course. I did not have the means to do a comprehensive count. It was just a feeling, based from the size of the venue and the density of the crowd, having attended so many marches before.
We started at about 3:30 PM, and it was quite orderly. The progress was slow because only one lane of Queen’s Road was reserved for the march. And we have to stop very often to let cars and pedestrians cross. Gradually I worked myself to the front of the march.
There were a variety of demands. But two major ones: fairly elections (one man one vote, and abolition of functional constituencies), and to free Liu. The marchers spanned quite a broad range: students, adults, seniors, men, women, Chinese, some Caucasions, ... I wish I can bring some of my students here. Perhaps some of them came by themselves. A university education is supposed to educate a person. Today, it has been reduced to academic learning, and even vocational training. It is a collective failure of the community, the university and us teachers. Some of us do try to do more, but it is not often appreciated.
There was a very heavy police presence, much heavier than previous marches. It was particularly noticeable towards the end, when we got close to the destination - China Liaison Office.
When I got out of the MTR at Charter Street, I found myself stuck in the middle of the crowd. I estimated the crowd to be about 10,000. It was not scientific, of course. I did not have the means to do a comprehensive count. It was just a feeling, based from the size of the venue and the density of the crowd, having attended so many marches before.
We started at about 3:30 PM, and it was quite orderly. The progress was slow because only one lane of Queen’s Road was reserved for the march. And we have to stop very often to let cars and pedestrians cross. Gradually I worked myself to the front of the march.
There were a variety of demands. But two major ones: fairly elections (one man one vote, and abolition of functional constituencies), and to free Liu. The marchers spanned quite a broad range: students, adults, seniors, men, women, Chinese, some Caucasions, ... I wish I can bring some of my students here. Perhaps some of them came by themselves. A university education is supposed to educate a person. Today, it has been reduced to academic learning, and even vocational training. It is a collective failure of the community, the university and us teachers. Some of us do try to do more, but it is not often appreciated.
There was a very heavy police presence, much heavier than previous marches. It was particularly noticeable towards the end, when we got close to the destination - China Liaison Office.
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