There is more to the sample size than the number 9. Every time unit before the experiment where the effects were not seen is a form of sample. For example, su

There is more to the sample size than the number 9. Every time unit before the experiment where the effects were not seen is a form of sample. For example, suppose nine old people took an unusual drug and then grew 1-3 inches over the next two years. The fact that it happened right after they took the drug, and not some other point in their life, would be one heck of a coincidence, the probability of which depends on the absolute rarity of that sort of event.