A Psychologist Wishes to Determine Whether Short-Term Memory Scores Are

A psychologist wishes to determine whether short-term memory scores are affected by the type of medication in hyperactive children. Sixty hyperactive children (30 boys and 30 girls) were randomly assigned to receive either Cylert or Ritalin (two kinds of amphetamines that are central nervous system stimulants) . Their short-term memory was tested on a 20-point scale (where 0 = no memory and 20 = perfect memory) . $\begin{array} { c c c c c c } \hline & \text { Boys } & && { \text { Girls } } \\\hline \text { Cylert } & \text { Placebo } & \text { Ritalin } & \text { Cylert } & \text { Placebo } & \text { Ritalin } \\\hline 12 & 5 & 3 & 5 & 4 & 12 \\10 & 6 & 2 & 6 & 6 & 9 \\13 & 7 & 5 & 2 & 7 & 14 \\10 & 6 & 6 & 4 & 6 & 13 \\9 & 4 & 1 & 3 & 5 & 9 \\12 & 5 & 4 & 2 & 4 & 12 \\13 & 6 & 2 & 4 & 5 & 8 \\10 & 7 & 6 & 6 & 6 & 15 \\11 & 5 & 1 & 2 & 7 & 12 \\12 & 7 & 5 & 4 & 7 & 11 \\\hline\end{array}$
-The results of Tukey's test for the main effect of drug levels reveal that

A) short-term memory is not different between Cylert and Ritalin conditions, but both are better than the placebo
B) short-term memory is better for Cylert than the placebo or Ritalin
C) short-term memory for Ritalin is better than for Cylert or the placebo
D) short-term memory is poorer for Cylert and Ritalin than for the placebo