-----Original Message----- Jeremy Bauer [mailto:[EMAIL PROTECTED]]
<snip> I have 10 subjects, each performing 2 different activities 10 times. I am looking at the difference in maximum left foot-ground forces during running and during landing from a jump. So, I measure foot-ground forces for subject A 10 times while running and 10 times while landing from a jump. I want to know if the maximum measured forces are different between tasks. <snip> In the past, I have calculated the mean foot-ground force for each subject in each task, then just used a paired t-test. This seems reasonable, however while no one has ever told me this approach is incorrect, no one has told me it is correct. I basically just don't have much confidence in that approach. <snip> -----Reply----- Brett Magill [EMAIL PROTECTED] So, you have a data set that might look somehting like the one beolow for two subjects? Do a google search for mixed effects (and/or random effects) models for repeated measures. Such a model would easily accomodate your design and has the benefit over taking an average by group across trials that it makes use of the extra information about variation within subjects. sub trial activity outcome 1 1 Running 0.40 1 2 Running 0.50 1 3 Running 0.49 1 4 Running 0.01 1 5 Running 0.93 1 6 Running 0.11 1 7 Running 0.47 1 8 Running 0.91 1 9 Running 0.47 1 10 Running 0.53 1 1 Landing 0.53 1 2 Landing 0.13 1 3 Landing 0.22 1 4 Landing 0.32 1 5 Landing 0.21 1 6 Landing 0.47 1 7 Landing 0.99 1 8 Landing 0.72 1 9 Landing 0.32 1 10 Landing 0.28 2 1 Running 0.13 2 2 Running 0.63 2 3 Running 0.83 2 4 Running 0.94 2 5 Running 0.70 2 6 Running 0.57 2 7 Running 0.47 2 8 Running 0.13 2 9 Running 0.69 2 10 Running 0.81 2 1 Landing 0.43 2 2 Landing 0.96 2 3 Landing 0.10 2 4 Landing 0.27 2 5 Landing 0.72 2 6 Landing 0.40 2 7 Landing 0.75 2 8 Landing 0.59 2 9 Landing 0.37 2 10 Landing 0.43 . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
