A cognitive psychologist investigates the effect of four presentation conditions on the retention of a lengthy passage describing the Battle of Gettysburg. Let us simply denote the presentation...

A cognitive psychologist investigates the effect of four presentation conditions on the retention of a lengthy passage describing the Battle of Gettysburg. Let us simply denote the presentation conditions as A, B, C, and D. Sixty-four (N 64) college students are randomly assigned in equal numbers to the four conditions (n 16). Memory is tested after students hear the passage read aloud one time. The depen dent variable is number of idea units recalled in the immediate written recall of the passage. The mean recall and standard deviation for each of the four pre sentation conditions are

A Calculate the 95% confidence intervals for the population means estimated by the four sample means.

B Interpret the pattern of confidence intervals by stating what we may conclude about the differences between the various population means.