Answer
$µ_{Pl}\neµ_{R~10~mg}=µ_{R~17.5~mg}=µ_{A~7.5~mg}=µ_{A~12.5~mg}$
There is enough evidence to conclude that Placebo group's score is less than the others groups' score.
Work Step by Step
In MINITAB, enter the Placebo values in C1, the Ritalin 10 mg values in C2, Ritalin 17.5 mg values in C3, the Adderall 7.5 mg values in C4 and in C5 enter the Adderall 12.5 mg values.
Select Stat -> ANOVA -> One-Way
Select Response data are in a separate column for each factor level.
In Responses enter C1 C2 C3 C4 C5
Click Comparisons. In "Error rate for comparisons" enter 5. In "Comparison procedures assuming equal variances" select Tukey. In "Results" select the 3 options. Click OK.
Click Ok.
