You are constructing a 90% confidence interval for the difference of means from simple random samples from two independent populations. The sample sizes are n1 = 6 and n2 =14 . You draw dot plots of the samples to check the normality condition for two-sample t-procedures. Which of the following descriptions of those dot plots would suggest that it is safe to use t-procedures?

I. The dot plot of sample 1 is roughly symmetric, while the dot plot of sample 2 is

moderately skewed left. There are no outliers.

II. Both dot plots are roughly symmetric. Sample 2 has an outlier.

III. Both dot plots are strongly skewed to the right. There are no outliers.

(a) I only

(b) II only

(c) I and II

(d) I, II, and III

(e) t-procedures are not recommended in any of these cases.

If the answer is e, why is a not correct?