A journal article reports a statistically significant ANOVA for four groups of n = 12 subjects with means of 1,5,7, and 8, with F = 3.86 > Fcrit = 2.82.
(a) Compute the width of the 95% confidence interval for a single mean. (b) Compute the width of the 95% confidence interval for the difference between two means. (c) Which of the six possible comparisons of two means would have 0 outside of the confidence interval for their difference?