Studying time to seed germination under several temperatures we may consider a germination box, for example, as an experimental unit. In this individual space, I sowed 100 seeds of one species at the same time. These seeds start the imbibition immediately, but the chemical reactions inside every seed depend on the physiological quality of every one. Thus, we have germination events at t1, t2, …, tn inside this germination box (the experimental unit). In the experiment, we can have j experimental units for every k treatments. The question is: may the researcher analyze this data set using a routine for repeated measures along the experimental time?
Dear Sir,
Usually, in germination tests you measure the gerimination percentage for each replicate (e.g. 4 batches of 100 seeds) and you estimate the mean value. then you compare the different means for the various temperatures.
Repeated measures are applied when you take measurements along time from the same experimental unit, but in my opinion this is not the case in your experiment. When a seed is considered germinated no further measurements are taken for this seed, and you continue your measurements for the rest of the seeds for a predetermined time period or a predetermined germination percentage (for germination rate).
Moreover you have to think of both gerimnation percentage (the total number of germinated seeds) and germination rate (how quick the seeds germinate), because under several temperatures you probably find differences in both values.
Hi
I think,
In repeated experiment, the mean analysis of each experiment you can compare with another set of experiment.
Finally which is significant one that you can propose..
Hi José,
as Spyridon said, you can not consider repeated measures. If you have only 100 seeds for each species, you should make 4 repetitions of 25 each, and use the mean, your result will be more robust. Pay attention to the diferences between the reps. For ISTA rules, you have to determine the difference of your mean germination with the max and the min, if it is too high, you can not, statiscally, use the mean. You have to begin again. See this link for more details.
Fabienne
Article Maximum tolerated differences between germination test repli...
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