The relationship between variance D (x) and the square of sample variance s, the relationship between sample mean and expectation Differences and relationships,

The relationship between variance D (x) and the square of sample variance s, the relationship between sample mean and expectation Differences and relationships,

In the case of average, the sample expectation is the same as the overall expectation, but not necessarily the same, because the sample may also be biased. Of course, the expectation of post statistics is different from the theoretical expectation
One difference between the sample and the population is the degree of freedom. If there are n values, the total experience requires that all n possibilities be considered, while the variance of the sample only considers n-1, because the variance of the sample focuses on the deviation degree, which can be understood as one of the default samples is the reference value, and the deviation degree of the other N-1 samples is calculated

For a group of data x1, X2, X3, x4, X5 arranged from small to large, where each data is less than - 1, then for sample 1, - x1, - X2, X3?
For a group of data x1, X2, X3, x4, X5 arranged from small to large, where each data is less than - 1, then for sample 1, - x1, - X2, X3, - x4, X5
For a group of data x1, X2, X3, x4, X5 arranged from small to large, where each data is less than - 1, then for sample 1, - x1, - X2, X3, - x4, X5, the median is -

For a group of data x1, X2, X3, x4, X5 arranged from small to large, where each data is less than - 1, the median of sample 1, - x1, - X2, X3, - x4, X5 arranged from small to large is X3, x5,1, - x4, - X2, - X1, and the median is (1-x4) / 2