The three major distributions are x~2 distribution, T distribution and F distribution, which together with normal distribution constitute the four major distributions in mathematical statistics. Statistics composed of standard normal population samples constitute the other three basic distributions in mathematical statistics.
Therefore, the normal population is always taken as the research object in mathematical statistics. In mathematical statistics, "population", "sampling" and "sample" are three basic concepts, quantile is the critical point of "small probability event", and confidence interval is the core calculation problem of parameter estimation and hypothesis testing.
K variables in contemporary numbers
The expansion of the sum of (P 1+P2+…+PK) n is a polynomial whose general term is the value given by the above formula. If these k variables happen to be the probabilities of possible outcomes, then the total value of these probabilities corresponds to the probability of an inevitable event. And the probability of inevitable events is equal to 1, then the polynomial above becomes (p 1+p2+…+PK) n =1n =1,that is, the value of the polynomial is equal to1.