Suppose you needed to test the claim that the two samples described below come from populations with the same mean. Assume that the samples are independent simple random samples.

Sample 1: $n_1 = 6, \ \overline{x}_1 = 21.8, \ s_1 = 9.68$

Sample 2: $n_2 = 13, \ \overline{x}_2 = 27.9, \ s_2 = 6.74$
Find:

(a) The estimated degree of freedom is

(b) The test statistic is (use Sample 1 - Sample 2)