Question

One of the primary advantages of a repeated-measures design, compared to an independent-measures design, is that it reduces the overall variability by removing variance caused by individual differences. The following data are from a research study comparing three treatment conditions.

treatment
A	B	C	P
6	9	12	27
8	8	8	24
5	7	9	21
0	4	8	12
2	3	4	9
3	5	7	15

           N=18, G=108, SUM=108

               

            

Treatment A: -

M=4

T=24

SS=42

Treatment B:-

M=6

T=36

SS=28

Treatment c:-

M=8

T=48

SS=34

a) Assume that the data are from an independent-measures study using three separate samples, each with n = 6 participants. Ignore the column of P totals and use an independent-measures ANOVA with alpha = .05 to test the significance of the mean differences.

b) Now assume that the data are from a repeated-measures study using the same sample of n = 6 participants in all three treatment conditions. Use a repeated-measures ANOVA with alpha = .05 to test the significance of the mean differences.

c) Explain why the two analyses lead to different conclusions.

Answer 1