## Question 882:

8. For the preceding problem you should find thatthere are significant differences among the three

treatments. The primary reason for the significance

is that the mean for treatment I is substantially

smaller than the means for the other

two treatments. To create the following data,

we started with the values from problem 7 and

added 3 points to each score in treatment I.

Recall that adding a constant causes the mean

to change but has no influence on the variability

of the sample. In the resulting data the mean

differences are much smaller than those in

problem 7.

I II III

n 6 n 6 n 6

M 4 M 5 M 6 N 18

T 24 T 30 T 36 G 90

SS 30 SS 35 SS 40 ΣX2 567

a. Before you begin any calculations, predict how

the change in the data should influence the

outcome of the analysis. That is, how will the

F-ratio and the value of η2 for these data compare

with the values obtained in problem 7?

b. Use an ANOVA with α .05 to determine

whether there are any significant differences

among the three treatment means. (Does your

answer agree with your prediction in part a?)

c. Calculate η2 to measure the effect size for this

study. (Does your answer agree with your

prediction in part a?)