In: Statistics and Probability
An independent sample experiment uses 25 participants in one group and 30 participants in the second group to compare the two population means. What is the degrees of freedom used in this test ?
a.
25
b.
24
c.
30
d.
29
For testing two population means we have two tests. One is used when population standard deviations are known and another is used when population standard deviations are not known. When population standard deviations are known we use the z test which will not have any degrees of freedom. But if population standard deviations are not known we have again two cases is., if the population variances are assumed equal and population variances are assumed unequal. In the first case, if population variances are assumed equal, we will have the t test with df where is the participants is first group and is the participants in the second group. Then according to the situation here, the df=25+30-2=55-2=53. Which is not given in the options. Now when population variances are assumed unequal then the formula for df contains standard deviations of the groups. The answer mainly is 53.