Question

The following data represent the results from an independent-measures experiment comparing three treatment conditions. Use SPSS to conduct an analysis of variance with α=0.05α=0.05 to determine whether these data are sufficient to conclude that there are significant differences between the treatments.

Treatment A	Treatment B	Treatment C
2	4	5
4	2	7
4	4	8
2	7	9
3	3	11

F-ratio =
p-value =
Conclusion:

• These data do not provide evidence of a difference between the treatments
• There is a significant difference between treatments

The results obtained above were primarily due to the mean for the third treatment being noticeably different from the other two sample means. For the following data, the scores are the same as above except that the difference between treatments was reduced by moving the third treatment closer to the other two samples. In particular, 3 points have been subtracted from each score in the third sample.

Before you begin the calculation, predict how the changes in the data should influence the outcome of the analysis. That is, how will the F-ratio for these data compare with the F-ratio from above?

Treatment A	Treatment B	Treatment C
2	4	2
4	2	4
4	4	5
2	7	6
3	3	8

F-ratio =
p-value =
Conclusion:

• There is a significant difference between treatments
• These data do not provide evidence of a difference between the treatments

Answer 1

a)

By using One-way ANOVA calculator:

Source	SS	DF	MS	F
Between-treatments	70	2	35	11.05263
Within-treatments	38	12	3.1667
Total	108	14

F-ratio = 11.05263

P-value = 0.001897

The result is significant at p < 0.05.

There is a significant difference between treatments.

b)

By using One-way ANOVA calculator:

Source	SS	DF	MS	F
Between-treatments	10	2	5	1.57895
Within-treatments	38	12	3.1667
Total	48	14

F-ratio = 1.57895

P-value = 0.246181

The result is not significant at p < 0.05.

These data do not provide evidence of a difference between the treatments.