The following are some historical cases.
Ratio of male to female at birth
Most people may think that the possibility of having boys and girls is equal, so it is inferred that the ratio of boys and girls should be 1: 1, but this is not the case.
In A.D. 18 14, the French mathematician Laplace (La Place 1794- 1827) recorded some interesting statistics in his new book "Philosophical Discussion on Probability". According to the statistics of London, Petersburg, Berlin and France, he got almost the same ratio of boys to girls. That is to say, among all the babies born, 5 1.2% are boys and 48.8% are girls. Strangely, when he counted the birth rate of boys in Paris for 40 years from 1745- 1784, he got a ratio of 25: 24, with boys accounting for 5 1.02%. Laplace is confused. He is convinced of the laws of nature, and he feels that there must be profound factors behind this 1.4%. So he made an in-depth investigation and finally found that Parisians at that time "preferred boys to girls" and abandoned boys, which distorted the truth of the birth rate. After the revision, the birth rate of boys and girls in Paris is still 22: 2 1.
An excellent mathematician = 10 teachers.
During World War II, the United States once announced that an excellent mathematician had a division of more than 10. This sentence has an unusual origin.
Before 1943, British and American transport fleets were often attacked by German submarines in the Atlantic Ocean. At that time,
Limited by their strength, Britain and the United States cannot send more escort ships. For a time, the German submarine war made the Allies at a loss.
To this end, an American navy general specially consulted several mathematicians. Mathematicians analyzed by probability theory that the encounter between the fleet and the enemy submarine was a random event. From a mathematical point of view, it has certain regularity. The smaller the fleet size of a certain number of ships (100 ships), the more times it is compiled (20 ships at a time, there must be 5 times). The greater the probability of meeting the enemy. The US Navy accepted the mathematician's advice and ordered the fleet to assemble in the designated sea area, then collectively pass through the dangerous sea area, and then separately sail to the scheduled port. As a result, a miracle appeared: the probability of the allied fleet being attacked and sunk dropped from 25% to 1%, which greatly reduced the losses and ensured the timely supply of materials.
What is a probabilistic weather forecast?
Probabilistic weather forecast is to express the possibility of forecasting quantity with probability value. What it provides is not the "yes" or "no" of a weather phenomenon, nor the "big" or "small" of a meteorological element value, but the possibility of a weather phenomenon. For example, for the prediction of precipitation, the traditional weather forecast generally predicts whether it will rain or not, while the probability forecast gives the percentage of possible precipitation. The greater the percentage, the greater the possibility of precipitation. Generally speaking, if the probability value is less than or equal to 30%, it can be considered that there is basically no precipitation; The probability value is 30%-60%, and precipitation may occur, but it is less likely; The probability is 60%-70%, and the possibility of precipitation is very high; The probability value is greater than 70%, and precipitation occurs. Probabilistic weather forecast not only reflects the certainty of weather change, but also reflects the uncertainty and uncertainty degree of weather change. In many cases, this forecasting form can better meet the decision-making needs in economic activities and military activities.
What is the probability of being infected with AIDS?
What is the probability of being infected with AIDS? According to Xu Keyi, director of ditan hospital STD Prevention and Control Center, AIDS is transmitted to others through three modes of transmission, namely blood transmission, sexual transmission and mother-to-child transmission. If a normal person transfuses the blood of an HIV-positive person or an AIDS patient, the infection probability is 95%, while an HIV-positive person or an already sick person has sex with a normal person, and the infection probability is related to gender. The probability of male transmission to women is 0.2%, and the probability of female transmission to men is 0. 1%, and the probability of male transmission to men is much greater than the above two methods. If the mother is HIV-positive or AIDS patient, the probability of fetal infection is 25%, but if the mother receives AZT treatment, the probability of fetal infection will drop to 8%. After combined therapy (cocktail therapy), the probability of fetal infection may drop to 2%.
HIV is a very fragile virus, which is very sensitive to heat and dryness. In a dry environment, HIV/KLOC-0 died in 0/0 minute and was inactivated at 60 degrees Celsius for 30 minutes. If a syringe with blood just touches the patient's body and immediately pierces a normal person, the probability of infection is less than 0.3%. It is for this reason that mosquito bites will not spread AIDS.
Intensive development, such as AIDS vaccine developed by traditional medical methods; The anti-HIV antibody developed by Chinese medicine technology and the "condom" advocated from the perspective of family planning all show us the dawn of defeating AIDS.
Do you know the probability of winning the lottery?
The probability of "7 out of 36" and "5 out of 26"
According to experts, the sports lottery "7 out of 36", Nanyue style "7 out of 36" and Nanyue style "5 out of 26" currently issued in Guangdong Province all belong to digital combination games, and their winning probability is calculated in the same way. Among them, the first prize hit probability of "7 out of 36" is 1/8347680, which is one of "5 out of 26" games. At present, the winning probability of the second lottery of the sports lottery "7 in 36" is still 1/8347680, the winning probability of the provincial special prize (with 8 numbers) of Nanyue style "7 in 36" is 1/32060340, and the winning probability of Nanyue Fuxing Award "7 in 36" is 9 numbers.
Life-threatening probability of smoking: 50% quitting smoking equals self-help.
1987165438+10. At the 6th International Conference on Smoking and Health held in Tokyo, Japan, the World Health Organization (WHO) suggested that April 7th 1988, the 40th anniversary of the founding of WHO, be the "World No Tobacco Day", and proposed that "Do you want to? 1989, the World Health Organization changed this day to May 3 1 day every year.
On May 3rd this year, we will celebrate the 7th World No Tobacco Day. However, the current situation of smoking in China is not optimistic: the number of smokers is increasing, reaching 320 million, the average age of smokers is decreasing, and the number of female smokers and teenagers is increasing.
Everyone has played the lottery. This game is very interesting and the fairest choice for everyone. Isn't probability used in it? Coin toss is also a form of lottery, but it is only a choice between the two, and the probability is different. The design of many games is either pure probability or cheating with probability. If you really want to play, of course, you must see the essence of things, otherwise you will be stupid.
These things mentioned above may be easy for everyone to understand, but some probability estimates make it impossible for everyone to draw more accurate conclusions, so more than N people are confused about it. For example, for a person who yearns for love, if you ask: What do you think is the probability that you will meet the ideal partner? How many people can answer. Of course, we can say that God has arranged another one for everyone, but this is a question of probability, not 100%. Also, how likely do you think he will become a rich man in the future? I guess this question is also a strange answer. Some people say it's impossible, really? Rationally speaking, anyone can develop, but he is dead. I mentioned the problem of blind date in my previous blog, and here we also look at its probability.