⑴ Simple random sampling: Generally speaking, if the number of people in a group is n, a sample with a capacity of n is extracted from it by the method of not putting it back one by one, and the chances of each individual being extracted are equal, which is called simple random sampling.
Note: ① The probability of each individual being drawn is;
② Common simple random sampling methods are: drawing lots; Random number method.
(2) systematic sampling: when the group is large, the group can be divided into several parts in a balanced way, and then according to the predetermined
Rule, extract an individual from each part to get the required sample. This sampling method is called systematic sampling.
Note: ①No.;
② subsection;
③ In the first paragraph, the number of individuals was determined by simple random sampling;
(4) Extracting samples according to preset rules.
⑶ Stratified sampling: When the known population consists of several parts with obvious differences, in order to make the sample reflect the overall situation more comprehensively, the population is divided into several parts, and then sampling is carried out according to the proportion of each part in the population. This kind of sampling is called stratified sampling.
Note: Number of people in each section = number of people in this section.
2. Estimation of total feature number:
(1) sample average;
(2) sample variance;
(3) Sample standard deviation =;
3, correlation coefficient (to determine the linear correlation between two variables):
Note: (1) > 0, the variables are positively correlated; & lt0, the variables are negatively correlated;
(2) ① The closer to 1, the stronger the linear correlation between the two variables;
② When it is close to 0, there is almost no linear correlation between the two variables.
Extended data:
The meaning of (1) algorithm, program block diagram.
(1) by analyzing the process and steps to solve specific problems (such as solving binary linear equations, etc.). ), we can understand the idea and significance of the algorithm.
② Through imitation, operation and exploration, experience the process of expressing and solving problems by designing program block diagram. In the process of solving specific problems (such as solving ternary linear equations, etc. ), understand the three basic logical structures of program block diagram: sequence, conditional branch and loop.
(2) Basic algorithm statements: Through the process of transforming the program block diagram of specific problems into program statements, we can understand several basic algorithm statements-input statements, output statements, assignment statements, conditional statements and loop statements, and further understand the basic idea of the algorithm.
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