In an online psychology experiment sponsored by the University of Mississippi, researchers asked study participants to respond to various stimuli. Participants were randomly assigned to one of three treatment groups:

Group 1, the simple group, required to respond as quickly as possible after a stimulus was presented; Group 2, the go/ no-go group, required to respond to a particular stimulus while disregarding other stimuli; and Group 3, the choice group, required to respond differently depending on the stimuli presented. The researcher felt that age may be a factor in determining reaction time, so she organized the experimental units by age and obtained the following data:

(a) What type of factorial design is this? How many replications are there within each cell?
(b) Normal probability plots indicate that it is reasonable to believe that the data come from populations that are normally distributed. Verify the requirement of equal population variances.
(c) Determine if there is significant interaction between stimulus and age.
(d) If there is no significant interaction, determine whether there is significant difference in the means for the three types of stimulus. If there is no significant interaction, determine whether there is significant difference in the means for the three categories of age.
(e) The residuals are normally distributed. Verify this.
(f) Draw an interaction plot of the data to support the results of parts (c) and (d).

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Stimulus Age (years) Simple Go/No-Go Choice 18-24 0.248 0.338 0.586 0.428 0.631 0.364 0.191 0.485 0.626 25-34 0.303 0.389 0.858 0.529 0.467 0.629 0.494 0.585 0.520 35 and older 0.384 0.567 0.302