A t-distribution is defined by one. N 1 N 1. T Value Table T Value T Test Statistics Statistics If the p-value that corresponds to the test statistic t with n 1 n 2-1 degrees of freedom is less than your chosen significance level common choices are 010 005 and 001. . The formula for Degrees of Freedom can be calculated by using the following steps. A two sample t-test is used to determine whether or not two population means are equal. For example the degrees of freedom formula for a 1-sample t test equals N 1 because youre estimating one parameter the mean. Find the degrees of freedom for a particular t test or confidence interval CI C I below. The degrees of freedom are based on. Here N N is the sample size. A t-test is the most commonly applied when the test. The degrees of freedom formula for a 1-sample t-test is N 1 since youre estimating one parameter the mean. This depends on the assumption whether t...