I have data set that includes:

  • multiple animals normalised heart rate
  • 2 trials for each animal
  • 3 time points per trial

I want to analyse this data by comparing mean heart rate at each time point across trials... So, I have no between subject factor and only within subject factors... This is apparently a two way within-subjects design however I have no idea how to run this in SPSS.

Can anyone help?


Sorry, I should have been more specific....

Animals were tested over two trials. I have taken raw heart rate and normalised it at 0.05 second intervals against the heart rate at the commencement of the each trial. From this, and based on previous literature, I have chosen 3 discrete time points in which to measure heart rate differentials between trials, 1 time point prior to the trial commencement, and two after (2 seconds prior, 2 second after and 7 seconds after).

I am looking to see if trial one, at 2 second after commencement differs from all other time points in both sessions.

Does this help?

  • 1
    $\begingroup$ If your repeated-measures data is "wide" form - you have 2x3=6 variables - go to GLM -> Repeated Measures. $\endgroup$
    – ttnphns
    Commented Sep 28, 2013 at 7:17
  • $\begingroup$ Why two-way? Please explain more about your variables. $\endgroup$
    – Vic
    Commented Sep 28, 2013 at 10:04

1 Answer 1


I can only guess at what "normalized heart rate" means. Assuming that is an appropriate dependent variable, at each time point get the difference between each animal's heart rates on the two trials, then do an ordinary repeated-measures anova on the resulting $n \times 3$ table. The test of the grand mean is really a test of the overall difference in heart rate between the two trials. The test of the time main effect is really a test of the trials $\times$ time interaction. A simple t-test of the mean at each time point is really a test of the difference between the trials at that time point.


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