Repeated Measures ANOVA – How to Handle Replicated Measurements

anovarepeated measures

I have performed an experiment testing 3 different modes of operation on 16 participants. Each mode of operation was tested twice per user. 

User    Mode    Trial1Time  Trial2Time
1       1       20          30
1       2       5           7       
1       3       40          25      
2       1       10          20
2       2       15          17      
2       3       30          35
3       1       13          26
3       2       11          11      
3       3       35          38

I have run repeated measures ANOVA on my data using only the Trial1Times. I would like to use both Trial1 and Trial2 in the analysis however as I have such a small number of participants.

  1. Is this possible with repeated measures?
  2. If so, does this add statistical power to the results?
  3. (Bonus) How would I go about doing this in SPSS?

Appendix: The data formatted in a different way (The actual numbers are different too, but I just made it up as an example)

User    Mode1   Mode1   Mode2   Mode2   Mode3   Mode3
        Test1   Test2   Test1   Test2   Test1   Test2
1       10      15      20      25      30      35
2       12      12      23      21      31      33
3       14      16      27      26      35      39

Best Answer

  1. Yes, this is very possible

  2. Yes, this will add power

  3. You'll need to format the data according to your second example to use SPSS repeated measures. Then you need to select Analyze -> General Linear Model -> Repeated Measures. In the Within-Subject Factor Name box, first type Mode and select 3 for number of levels, then click add. Then enter Time into the Factor Name box, select 2 for number of levels, and click add. Then click 'Define'. You should be able to select the six variables you've created and they'll slot into the right within-subjects boxes. Then just adjust any settings you want, click OK, and you'll have the analysis you want. Here's the syntax, though for slightly different variable names:

    DATASET ACTIVATE DataSet0.
GLM Mode1.Trial1Time Mode1.Trial2Time Mode2.Trial1Time Mode2.Trial2Time Mode3.Trial1Time Mode3.Trial2Time
/WSFACTOR=Mode 3 Polynomial Time 2 Polynomial 
/METHOD=SSTYPE(3)
/CRITERIA=ALPHA(.05)
/WSDESIGN=Mode Time Mode*Time.
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