Timeline for How to choose the sample size for a pilot study for making a power analysis?
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| Apr 13, 2017 at 12:44 | history | edited | CommunityBot |
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| Jun 21, 2015 at 11:34 | comment | added | EdM | In the page linked from the first paragraph of this answer, there is prior information not only on the effect size but also on the standard deviations of the values, and there is an assumption of normally distributed values. Simulations also require similar information and assumptions, although the yes/no dichotomy of responses analyzed by logistic regression may simplify this process a bit. | |
| Jun 21, 2015 at 7:46 | comment | added | mmh | Thanks for explaining. I think I got your point now (reading the answer by @stockhazesthai helped as well). | |
| Jun 20, 2015 at 13:22 | comment | added | stochazesthai | Well, you are designing an experiment so that IF you hypothesize a certain effect size, you need a sample size pf N to achieve a power of 0.8 and a significance level of 0.95. I mean when you are designing an experiment for a new drug that should reduce the mortality you don't have previous studies but you guess an effect size in order to design the experiment. | |
| Jun 20, 2015 at 13:16 | comment | added | mmh | If you are studying something new, how could you have an expected effect size? It would be just pure guessing without a pilot study. Though, I don't know how to answer the question. | |
| Jun 20, 2015 at 13:16 | comment | added | stochazesthai | Moreover, if the sample size is 4 per group the effect size needed to achieve a 0.8 power should be huge... | |
| Jun 20, 2015 at 13:15 | comment | added | stochazesthai | Yes, but I mean you can do an hypothesis on the expected effect size! | |
| Jun 20, 2015 at 13:07 | comment | added | mmh | Power analysis needs an estimate of effect size. Without any previous data, one does not know it. | |
| Jun 20, 2015 at 11:56 | history | answered | stochazesthai | CC BY-SA 3.0 |