The concept and calculation formula of difference, for example, the scores of two people in five exams are as follows: x: 50, 100, 100, 60, 50, and the average e (x) = 72; Y: 73, 70, 75, 72, 70 Average E(Y)=72. The average score is the same, but x is unstable and deviates greatly from the average. Variance describes the deviation between random variables and mathematical expectations. A single deviation is the average of the square deviation, that is, the variance without the influence of symbols, which is recorded as E(X): the direct calculation formula separates the discrete type from the continuous type.
The mean square error is the standard deviation calculation δ, which depends on whether the sample size is equal probability and probability. If there is no probability, directly calculate the square of deviation = (sample size-average) square, then sum the square of deviation of sample size, divide it by (sample size-1), and then open the root sign, which is the standard deviation. If there is a probability, you only need to consider the weighted average when calculating the total number, instead of dividing by the number-1, and directly open the root sign.
The standard deviation, also known as the mean square error, is the average of the average distance of each data. It is the square root of the average sum of the average variance, expressed by σ. The standard deviation is the arithmetic square root of variance. The standard deviation can reflect the degree of dispersion of the data set. If the average value is the same, the standard deviation may be different.
How to learn math well
1. Establish a solid foundation: Mathematics is a subject gradually based on basic knowledge. Make sure that you have a deep understanding of basic mathematical concepts, operation rules and formulas, and lay a solid foundation for learning more advanced mathematical content.
2. Mastering problem-solving skills: Learning mathematics well is not only remembering formulas and definitions, but also mastering problem-solving skills and methods. Understand the ideas and methods of solving different types of problems, and skillfully use various problem-solving skills, such as analyzing problems, finding laws, applying mathematical tools, etc.
3. Pay attention to practice and practice: Mathematics is a highly practical subject, and you should improve your mathematics ability through practice. Do more exercises, examples and mock exams to deepen the understanding of concepts and improve the speed and accuracy of solving problems.