The calculation method of degrees of freedom depends on the statistics and data types studied. The following are some common calculation methods of degrees of freedom:
1. Sample variance and standard deviation: For the population sample from normal distribution, the denominator of sample variance and standard deviation is n- 1, where n is the sample size. Therefore, the degree of freedom of sample variance and standard deviation is n- 1.
2.t-test: For single-sample T-test, the degree of freedom is equal to the sample size minus one; For independent two-sample t-test, the degree of freedom is equal to the sum of the two sample capacities minus their difference minus one; For paired two-sample t-test, the degree of freedom is equal to the sum of two sample sizes minus one.
3.f-test: The calculation of the degree of freedom of F-test is complicated and needs to be calculated according to the research design and formula. Generally speaking, the total degree of freedom is equal to the sum of the degrees of freedom of each independent variable MINUS the degrees of freedom of the interaction term.
4. Chi-square test: The degree of freedom of Chi-square test is equal to the sum of squares of observed frequencies minus the expected frequency.
5. Regression analysis: The degree of freedom calculation in regression analysis is also complicated and needs to be calculated according to the research design and formula. Generally speaking, the total degree of freedom is equal to the number of independent variables MINUS the degree of freedom of constant items in the model.