6. two separate samples receive different treatments. after treatment, the first sample has n = 9 with ss = 462, and the second has n = 7 with ss = 420. a. compute the pooled variance for the two samples. b. calculate the estimated standard error for the sample mean difference. c. if the sample mean difference is 10 points, is this enough to reject the null hypothesis using a two-tailed test with α = .05? gravetter, frederick j. statistics for the behavioral sciences (p. 329). cengage learning. kindle edition.