In the pavilion, a lecture was underway. Chen Hua, who sent information to Yuwen Wen, listened to Yuchi Mingyue's lecture, who had a little success in practicing the "magical magical skills". What Yuchi Mingyue said was "mathematical statistics".

Mathematical statistics are a branch of mathematics. Based on the theory of probability, they study the statistical regularity of a large number of random phenomena.

To conduct mathematical statistics, you need to collect various types of data, then sort them out and group them. Based on the various data, the overall population is inferred and predicted based on the regularity summarized by the data.

Yuchi Mingyue blew the role of mathematical statistics so that there was nothing on the earth, and Chen Wu didn't believe it.

Chen Hua believed that learning general arithmetic well is enough, so why bother to learn mysterious "probability theory" and "mathematical statistics". Yuchi Mingyue couldn't say much of the big truth in an anxious manner, so she refuted Chen Hua's view.

After thinking for a while, Yuchi Mingyue asked a question:

A certain train is driving on a certain railway. When you go from A to B, you have to know the train, so the speed is slow, with an average speed of 30 miles per hour. When you go from B to A, you don’t need to know the train, so you have a fast speed of 60 miles per hour.

So, what is the average speed of the train going back and forth on this railway?

Chen Wu thought about it and replied: "The average speed is 45 miles per hour."

Yuchi Mingyue shook her head: "Wrong, the average speed is forty miles per hour."

Chen Wu was dissatisfied: "This is wrong. Thirty plus sixty, and then divided by two, isn't it forty-five? How to calculate forty?"

Yuchi Mingyue replied: "You are calculating the arithmetic average, but the average is not only arithmetic average, but also geometric average, countdown average, etc. The question just now needs to be calculated using the countdown average..."

"The reciprocal average is suitable for calculating the average value of different round trip speeds on the same road section, so this question should be to first reverse the two numbers, calculate the sum, and then... the formula is like this..."

Yuchi Mingyue wrote the equation on paper: 2 /(1/30 + 1/60)=40

"This problem must be calculated using the countdown average, otherwise, if railway managers make decisions based on the arithmetic average, many difficult-to-explain problems will arise."

Chen Wu thought about it for a while and suddenly realized: "So that's it, what is that geometric average?"

Yuchi Mingyue was not in a hurry to answer, and asked another question: "Suppose we have a five-year deposit with a principal of 100,000 yuan (100,000,000 yuan, that is, one hundred coins), and it has a bank or cabinet, and its annual interest rate will change..."

She picked up the pen and wrote on the paper, and said while writing: "Suppose, the annual interest rate is: 1%, 9%, 6%, 2%, 15%..."

"Now, we want to calculate the average annual interest rate and calculate the sum of principal and interest in five years based on this, so how should we calculate it?"

Chen Hua knew how to calculate this application problem. She raised her pen and wrote the formula as she said: "Multiply the principal continuously by the annual..."

"So the calculation process is: 100000x 1.01 x 1.09 x 1.06 x 1.02x1.15 = 136883.70."

Yuchi Mingyue nodded and said, "There is another way to calculate, do you know?"

Chen Wu thought for a while: "Uh...use the average?"

She saw the other party nodding, so she picked up the pen and wrote another formula: "We should ‘average’ interest rates for the past five years..."

"If written as a formula, it should be (0.01 +0.09 +0.06 +0.02 +0.15)÷ 5 =0.066, that is, 6.6%..."

Chen Wu picked up a new multiplication calculator (hand-cranked) and shook it: "Then we substituted the average interest rate into the compound interest calculation formula: 100000x(1.066^ 5 - 1)+ 100000 = 137653.11...Hey? Why... Why are there more than 700...700 texts?"

She put down the calculator and looked at Yuchi Mingyue in confusion.

"You also found something wrong, right? Where is the problem?" Yuchi Mingyue asked first and then answered. "This algorithm made a common mistake: applying the addition operation to the multiplication process, the results obtained are of course inaccurate."

After Yuchi Mingyue finished speaking, she took out another piece of paper to start formulating: "Then, let's try to calculate the average annual interest rate using geometric averages..."

"1.01 x 1.09x 1.06 x 1.02 x 1.15 = 1.368837042"

"Put the result into the 5th power square root, then you will get the geometric average..."

Yuchi Mingyue used a new root number calculator (hand-cranked) to calculate it. After shaking it for a while, the calculation result was: 1.064805657, about 1.0648.

Shake the multiplier calculator again: "We substitute this geometric mean into the compound interest calculation formula: 100000 x(1.0648 ^ 5 - 1)+ 100000 = 136883.70"

"Look, isn't this the same result as the yearly calculation?"

Chen Wu looked carefully for a long time, and finally realized: "So that's it!"

Chen Hua often used to deposit money in Xingchang Bank. Based on her absolute trust in Xingchang, she asked the salesperson to give the sum of the principal and interest after the deposit expired, so she was not clear about the specific average algorithm.

Yuchi Mingyue smiled and said, "So, you can't simply add the data and divide it by the total number of data as soon as you see the word 'average'. In this way, you calculate the arithmetic average, and many places need to use geometric averages or reciprocal averages."

"These are all nouns and algorithms in mathematical statistics. Although ordinary people don't need it very much in daily life, they are used to do business and business. "

Yu Wen, who has been the audience, finally had the opportunity to speak. He looked at Chen Wu and said, "Yes, don't underestimate these two studies, it's really a powerful tool for making money, such as selling insurance..."

"The risk of insurance underwriting, that is, accidents, happen immediately, so there is a probability of occurrence. Then, the premium and odds calculation based on probability theory are an amazing science."

"If probability theory is used well, insurance companies can ensure that they make steady profits and make a lot of money."

"Similarly, mathematical statistics can solve investment problems, allowing people to determine the best investment plan through mathematical calculations from different investment plans. There are many examples of this, and it can't be finished after a few nights."

Chen Wu believed in Yuwen Wen the most. Hearing his husband's "blow" so much, he couldn't help but sigh: "These two subjects are so important. Will they also need to take the imperial examination in the future?"

Yuwen Wen shook his head: "There is no need for this. This is already a professional field of knowledge. Students who take the imperial examination only need to know the relevant concepts and simple applications."

"If you have a specialty in your profession, you will likely not be able to use this kind of knowledge after becoming an official, which will reduce your learning efficiency. However, if you want to follow the technocratic route, you must learn it."

"Or, those who only know how to do academic disciplines and are not good at being officials can also consider making a living by relying on mathematics."

Chen Wu was a little curious: "Math is your business? How do you say this?"

Yuwen Wen carefully placed two expensive hand-cranked computers and said with a smile: "It's very simple. In Huangzhou, many of the difficulties encountered by industry and businessmen will be offered rewards in the state. Mathematicians or scholars proficient in mathematics will be asked to solve them. As long as someone solves them, the reward will be obtained."

"Those who are addicted to mathematics can serve as teachers, have a stable job and income, and then work with fellow friends to develop technical problems based on suspense issues released by the Chamber of Commerce."

"It doesn't matter if you can successfully research and give me some rewards, but if you fail to solve the problem, it doesn't matter. Being able to study and discuss mathematical problems with fellow friends can also make mathematical enthusiasts happy."

"This atmosphere has lasted for more than 20 years. Many valuable mathematical formulas were born through rewards. Relying on these scientific solutions, the rewarders have solved countless difficult problems and made considerable economic profits."

"At the same time, many mathematicians and enthusiasts have continued to improve their theoretical level and discovered many new theories and formulas. More importantly, knowledge can be used to exchange for a decent life, which has left many scholars who are obsessed with academic research completely without any worries."

"In Huangzhou, a large number of mathematicians, scholars and enthusiasts gathered, who regularly hold academic conferences and constantly improve various mathematical theories."

"At the same time, many people make their fortunes by relying on mathematics, supporting the whole family alone, able to use air conditioners in summer and heating in winter, becoming a dazzling role model."

"Those industrial and commercial workers who use mathematical knowledge to solve economic problems also become role models in the eyes of their peers with their excellent performance."

Speaking of this, Yuwen Wen was a little happy: "The power of role models is huge. Scholars rely on knowledge to make a living, and merchants rely on mathematics to make a lot of money, so that more and more people can devote themselves to the study of the profound science of mathematics, without the need for the court to mobilize."

"More and more businesses are learning to solve economic problems in math. People who are proficient in math are becoming more and more popular. What does this mean?"

"It means that mathematics, as the foundation of science, is being taken more and more seriously because it is practical. With the rapid development of the economy and driven by huge benefits, it will accelerate the development of the science of mathematics and promote the development of other disciplines."

Chen Wu was quite interested when he saw Yuwen Wen's statement of mathematics so bright: "Then, is Erlang teaching the probability theory of concubines?"

"Ah? Ah... OK..." Yuwen Wen's tone fell a lot in an instant. Yuchi Mingyue didn't know that her husband was a half bucket of water in this regard, so she also struck while the iron was hot: "Erlang! I also have many problems that I can't figure out, so I have to give some advice to me..."

"Uh..." Yuwen Wen was unwilling to admit that he was a "believed" in this regard. It was difficult to refuse due to face. After thinking about it, he thought of a way to escape: "Have you ever heard of a theory?"

Chen Yao and Yuchi Mingyue asked together: "What theory?"

Yuwen pretended to be mysterious: "That is...wave-particle duality..."
Chapter completed!