Writing Paradox

people are used to give judgement/conclusion, before they have the reasons.

students are taught to have reasons, then follow logic (the way of manipulate reasons), thus have judgement or conclusion.

in every writing lesson, teachers must teach you, write the sentence statement at the very beginning, which mean, you should have a judgement, before everything. even when you write down you outline, you are taught to have judgement/view point before.

This is totally wrong!!! we should write in an opposite way. start with reason, then conclusion.

Distinguish of HyperGeometric , Binomial and Poisson Distribution

First , Let me give definition of them by when to use.

HyperGeometric (HG) = when the events are not replaceable. ( like pick cards) i.e. events are related.

Binomial (BI) = when events are replaceable. ( like toss coins) i.e. events are not related (mutually exclusive)

Poisson ( pronounce: po song ) (PS) = when events are counted continuously and in term of interval. (like How many cars pass the lines in given time interval)

HG and BI are closely related as we can see, just a matter of replaceable or non-replaceable. But why PS also related?? Before, we should know HG and BI, how exactly they are related.

Lets take an example of cards drawing.we have 52 cards. the probability of pick 2 hearts out of 5 draws is:

5C2 * (13/52) (12/51) (39/50) (38/49) (37/48) = 0.27

or using Excel =HYPGEOMDIST(2,5,13,52)

because every time you pick up a card, there is 1 card less in the sample space.

how about we pick out 52 cards, all of them? of course, we will have 13 hearts, no more, no less.

HYPGEOMDIST(13,52,13,52) = 1

ok, now, if we have infinite number of cards, and, the proportion of heart is still a quarter, what is the probability of 2 hearts in 5 draws?

is HYPGEOMDIST(2,5,inf/4,inf) ???

since there are infinite number of cards, the statement of non-replaceable is making no sense. Thus, it become BI

5C2 (1/4) (1/4) (3/4) (3/4) (3/4) = BINOMDIST(2,5,0.25,0) = 0.26 little bit less, but it is NOT because the huge sample space reduced the chance.

OK, i assume, you got the idea that, if the sample space goes to infinite, or real large, HG is BI. i say, if sample space is 500 times larger than the pick up size, then, it is safe to use BI to replace HG.

We can related BI to PS now.

Let takes an example to show the different.

in 100 people, 30 are boys . the probability of getting 3 boys in 10 people is follow BI or HG more accurately.

if someone using Poisson, he is assuming that, there is probability that we can get 11 boys by picking 10 people out!!

One thing we can see is, in Poisson Distribution, the event of success (boy) should not be bounded by the sample space (people picked) . or we can say,

in Binomial, number of boys <= number of people picked.

in Poisson, number of boy can any number.

so, if the number of pick goes to infinite in a given interval, or counted continuously . thus, BI goes to PS.

one sample is monitoring, we detect signal in any time.

like the number of leak in 1 km of water pipe. first, the leakage is not bounded by the length of water pipe. Second, we pick event in every where. Thus, we use PS.

But if we divide the water pipe in 100 equal intervals, and we want to know how many intervals are leaking. thus we should use BI, or HG.

A short summery,

sample space = N (people, cards)

pick put size = n

target size = T (boy, heart)

interested size = x

HYPERGEODIST(x,n,T,N) = Probability of x heart out of n pick out, where there are T hearts and N cards, with out replacement.

BINOMDIST(x,n,T/N,0) = Probability of x heart out of n pick out, where there are T hearts and N cards, with replacement. ( when T/N is a constant, and N goes to INF, HG goes to BI )

POISSON(x, n T/N,0) = Probability of x heart out of N intervals, where nT/N is the mean. ( when nT/N is a constant, n and N goes to INF, HG or BI goes to PS )

Integrated Task

Author said, using cell phone on driving cause accidents, because driver’s attention was distracted. That’s why governments over the world have posted restriction on cell phone usage while driving. The restriction may vary in different places. Some are totally prohibited the use of cell phone during driving, some are allowed the use of cell phone with hand-free devices. In additional, automobile insurance will be lost if the accident is involved talking on cell phone.

However, the speaker stated that using of cell phone is not strongly related to car accident. Traffic accidents are also caused by other issues, like talking with passengers, eating, making up or even attend to children. A research on driver by video recorded driver’s behavior revealed that most car accident is mainly caused by different kind of distractions like looking at GPS device. At the end, speaker suggested that cell phone actually safe life or even reduced road accidents. Drivers can use cell phone to make emergency call, report road accident and possible road hazard.

What invention is the most important in 20 century? II

I believe electronic devices are the most important invention in 20 century. Because it is so close to our daily life and completely changed our society. Have you heard about EM bomb? It is a bomb that can burn out all electronic devices without killing people. Many governments are restricted that kind of bomb, although it is not harmful to human. We can see how important electronic devices affected us.

Electronic devices are important because of the programming power. A program can handle special situation when designed input was detected. Like in the supermarket, when the bar code scanner detected a code, the price and the information of the goods were shown up in the screen and calculated the total price. That is the power of programming. Nowadays, nearly almost anything can be programmed. And it saves a lot of time.

Electronic devices also have the power of calculation. It can do million and million calculations in just 1 second. The influence is deep and width. In logistic industry, hundreds and hundreds of goods and cargos are needed to be transported. With the help of electronic devices, every goods and cargos are labeled with a signal emitter, when someone needs to check how many things are in there, they simply check how many signals were received and compare it to the database. It cannot be done within few seconds in the past. Another example is research and stock markets. Researcher can now study some difficult and complex problem by the aid of computers. The stock markets need to process a lot of trading in a short time. All of this cannot be done without electronic devices.

Today, we can see electronic devices are everywhere. In the car engine to cell phone, from shopping malls to stock markets, from entertainments to research fields, none of these are able to work in modern society without it, not just because it is convenient, but also it can handle massive calculation.

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An American or a chinese roommate.

If I can choose, and if I can only have 1 single roommate, then I prefer to have an American roommate, rather than a Chinese. It is because an American roommate can bring culture different and inspire new ideas. Although living with a roommate who has same culture is easy, because we share similar living style, it wasted a chance to learn something new. And most importantly, throughout my life, i probably will work and live with Chinese rather than American. So it is a very valuable time for having an American roommate.

As we know, every culture has advantages and disadvantages. In order to discover and improve our weakness, the best way to do is through comparison. I am a Chinese, who has a long history behind of me, while compare to an American, they hay rather short history. My long history background may possibly make me conservative, like obey authority, lack of innovations and not independent, while our American counterpart may be totally different. I believe living with an American will be a wonderful experience.

Nowadays, due to the economic bloom in china, many westerners proposed an imaginary threat from china. It is natural to be afraid in front of something unknown. So, I believe it is because we do not understand each other very well. The best way to know each other is living together. Therefore, having an American roommate is not a good for me to learn from American, but also the best way to let American learn from me. I believe through the culture exchange, both of us will learn a lot, and most importantly, friendship and trust and be found.

All in all, I will choose an American roommate rather than a Chinese. Not because I like the western style, but it is a good chance to let 2 cultures fusions together.

What invention is the most important in 20 century?

A truly important invention should not only bring us good things, but also bad things, and also make a deep influence to us. Therefore, I think airplane is the most important invention in the 20th century. Although it is not a new idea that moving in the sky, airplane is realized in this century. At the beginning, airplane is only for army. But after while, it become commercialized that not just transporting goods or letters but also people.

Airplane is so important because it lets people able to go around the earth fast. One direct effect is the tourism. People start to travel, understand different culture and make friends at different nations. This brings understanding and open up mankind’s mind. People now know that every people, cultures are valuable. No one is superior then others. Now a day, we will solve conflict by negotiation rather than fight. This is because of understanding.

Airplane also transports goods as well. California fruits can be tasted in Hong Kong at the same season. People can now do business around that world, because good can be transported fast. The most important influence is that, life-saving material can be delivered faster and quick into area of natural disasters, incidences and accidents.

Airplane also gives a lot inspiration. When we start to explore the sky, we are able to study our planet from above. We are now in a better position to predict the weather. By take photographs of our earth, we are able to “see” the human activities, like urban expansion, water reservation.

Besides of the good it brought, there is also bad thing. We can see this in the World War II. That war is the first time human fight in the sky. Troops and booms can now be transported fast and conflict and dead may happen without any prediction.

Airplane has already changed our way of life in many different aspects. From food to cloth, form business to friends, either good or bad are all affected by this convenience and fast machine. Next time, when traveling around, think about airplane.

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