QUESTION 7 2.25 Given X1 = 18, N1 = 12; X2 = 19, N2 = 5,5x1-x2 = 2.5 a=0.05, 2 tail. Our conclusion would be: since df=15, reject the null since df = 15, retain the null since df = 17, reject the null. since df =17, retain the null