Hi all, I am currently doing a study on cognitive behavioural therapy(CBT) on POI patients, and my null hypothesis is that CBT improves QOL in these patients. my primary outcome would be the general health(GH) portion of the SF-36 questionnaire. Based on previous research done, the standard deviation for GH of PCOS patients were 21.74, and the minimal clinically significant difference is 5 points. Assuming 80% power and 5% significance level, do I have enough information to calculate sample size? Ive read through multiple papers but all of them have different methods to calculate. Do I have to take into account intraclass correlation or variance inflation factor?
Well I have heard male residents say cystitis doesn't need treatment and have heard female residents say you'd treat it if you had it. So,
a larger sample is likely better than a small one. For your calculation you might Google Gpower and the relevant literature. But a pilot sample may be really helpful. May the force be with you. David Booth
BTW I am not familiar with the instrument you will use but Rosner Fundamentals of Biostatistics may be a good reference for you.. remember regression method depends on properties of your DV. It is unlikely that your DV will meet the requirements for ordinary least squares regression. So check Rosner for your type of regression. Good luck
David Booth
You also need to tell us the minimum effect that you would like to be able to detect with 80% probability (assuming your assumptions are okay).
You also need to tell us about your design. For example, are your data independent or for example are you sampling people from ten clinics. How are people being allocated to the CBT versus the control group?
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