15. A psychologist would like to examine the effects of a new drug on the activi

Question

15. A psychologist would like to examine the effects of a new drug on the activity level of animals. Three samples of rats are selected with n=5 in each sample. One group gets no drug, one group gets a small dose, and the third group gets a large dose. The psychologist records the activity level for each animal. The data from this independent-measures experiment are presented below. Conduct an ANOVA to determine whether these data indicate any significant differences among the treatments. Use the four steps of hypothesis testing to complete the ANOVA summary table, test your hypotheses, and make a decision.

No Drug Small Dose Large Dose

5 5 10

1 9 9

1 6 6

5 5 8

G=90 3 5 12

X2= 678

T1=15

T2= 30

T3= 45

SS1=16

SS2= 12

SS3= 20

H0: ________________________ H1: ____________________________________________ Show all your work and write your final answers in the ANOVA summary table below! Source SS df MS F Between treatments Within treatments Total Decision (check one) : ____ reject H0 ____ fail to reject H0 *Fcrit = _________ Conclusion (check one) :_____ there is a significant difference among the effects of the treatments ____ there is not a significant difference among the effects of the treatments *Would it be appropriate to compute post hoc tests based on these results? ____ Yes ____ No

Explanation / Answer

The hypothesis of testing is:

F critical = 3.8853

Since F > F critical, we reject H0.

There is a significant difference among the effects of the treatments.

Yes, it be appropriate to compute post hoc tests based on these results as we reject H0.

ANOVA Source of Variation SS df MS F Between Groups 90 2 45 11.25 Within Groups 48 12 4 Total 138 14

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