PSY340: Statistics for the Social Sciences

ANOVA: Analysis of Variance Homework#2

1) What advantages does a repeated-measures design have over an independent-measures design? What disadvantages are there?

2) A researcher used an analysis of variance to evaluate the results from a single-factor repeated-measures experiment. The reported F-ratio was F(2,28) = 6.35.

a) How many different treatment conditions were compared in this experiment?

b) How many subjects participated in the experiment?

c) With an alpha level of 0.01 would you reject or fail to reject the null hypothesis?

3) The following data were obtained from a repeated-measures study comparing three treatment conditions.

	Treatments
Subject	I	II	III	person totals
A	6	8	10	24
B	5	5	5	15
C	1	2	3	6
D	0	1	2	3
condition totals	12	16	20
condition SS	26	30	38

a) By hand, test the null hypothesis with an alpha level = 0.05. (show your work, state your tested hypothesis). Present your results in an ANOVA table.

b) Check your work by entering the data into SPSS and performing the ANOVA. Print out the output and attach that to the homework.

c) If you had gotten the exact same data, but from a between-subjects design. What would your observed (computed) F-ratio have been? (hint: you can figure this out from the information in your ANOVA table for part a). Would you have come to the same conclusion about your null hypothesis?

4) The following summary table presents the results of an ANOVA from a repeated-measures experiment comparing four conditions with a sample of 10 subjects. Fill in all of the missing values in the table.

Source	SS	df	MS	F-ratio
Between treatments			20
Within treatments
Between subjects	36
Error
Total	150