Use the t-distribution table to find the critical values for the indicated alternative hypothesis, level of significance, a and sample size n1 and n2. Assume that the sample are independent, normal and random. Ha: u1 < u2, a = 0.25, n1 = 9, n2 =6.
a) Find the critical values assuming that the population variance are equal.
b) Find the critical values assuming that the population variance are not equal.