Oh, dear. Where to begin? To deal first with your explicit question, the obvious analysis would be a two-way (8 conditions by 10 repetitions) analysis of variance (ANOVA) without interaction (because with only 1 observation in each of the 80 cells you cannot simultaneously measure both a systematic interaction effect (with 7x9=63 degrees of freedom) and random error variation). "Conditions" are probably <fixed effects> and "repetitions" <random effects>, but it is imaginable that the conditions are also random; you don't supply enough detail to tell. The problem is formally equivalent to a <one-way randomized blocks> design (with "repetitions" as the blocks), if that's any help in consulting statistical references.
The hard part, however, will be interpreting whatever results you get. Interpretation will depend considerably on how you actually conducted the experiment. A. Suppose, e.g, you set up Condition 1 and carried out the 10 repetitions; then set up Condition 2 and did 10 repetitions; and so on. Your dependent variable is the time taken to perform a task. Since performance often improves with practice, the time at the end of the ten repetitions may well be systematically less than the time at the start (although it might be unlikely for the decline in time to be _linear_ with the number of repetitions). So you would not be surprised to find that this improvement was regular enough to be detected at a reasonable significance level. But what of the conditions? Possibly practice on Condition 1 (or in general the earlier conditions) helps to improve performance (that is, to decrease the time needed to perform) on Condition 2 (or in general the later conditions). Then you cannot trust a result that tells you your performance under Condition 10 (e.g.) took less time than under Condition 1 (or in general any earlier condition). B. Or suppose you performed under Condition 1 once, then performed under Condition 2, and so on; then for the second repetition you encountered the eight conditions in the same order; and so on. Again, you cannot trust any apparent significant _decline_ in performance time from Condition 1 to Condition 8, although it is possible that the effect of prior practice might be somewhat subtler in this case than in case A. C. If you carried out the experiment as in B, but at each repetition you varied the order of the conditions (either randomly or in some counterbalanced order -- either is arguable, and superior to B), you might more reasonably trust any difference(s) you found as a function of conditions. As in B, the practice effect of repetitions might be washed out a bit by whatever interference is generated by the different conditions, but one would still expect there to BE a practice effect, if not necessarily a detectable one. Any further comment would require sheer speculation on my part. On 10 Jul 2003, Pingu wrote: > It has been many years since my pschology degree and i can now > finally say that the last remnants of all stats knowledge i once had > have now vanished. Recently i have started running experiments again > and need to analyse my data - but i can't figure out which analysis > to run. Any help would be greatly, greatly appreciated. > > Basically i have 8 conditions, and within each condition i measured > the time it took me to perform a task, which i repeated 10 times. I > now want to analyse the data to see whether any of the conditions > lead to significantly faster response times than the others. I am > sure i remember doing some analysis which measured all conditions > against all others, but i just can't remember what it was. I have > SPSS but still nothing is jolting my memory. ----------------------------------------------------------------------- Donald F. Burrill [EMAIL PROTECTED] 56 Sebbins Pond Drive, Bedford, NH 03110 (603) 626-0816 . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
