rct??

[bekib86]

Dont know if this is the right section to post this but can a Random Controlled Trial have their subjects randomly chosen if there is criteria to meet?? Thanks

[bednobs]

most likely, they select the participants according to the criteria, then they randomise those participants to the groups of the trial. For example, an rct to see which weight loss programme works better, like the bbc diet trials a few years ago was carried out on obese people with no co morbidities ... they advertised for these people, the randomised them into 5 groups (4 different diets and a control group). this was a true randomisation of the participants, who were picked according to the criteria

[bekib86]

Oh right i see, thanks. can you help me with my other question?
What does this sentence mean in an RCT report?

Using a conventional 5% two sided test, with 80% power, the sample size required for prevalences of 50% and 60% in two groups was 388 per group (total 1164)

I do not understand this at all and I need to report whether the sample size was justified in my critique of the whole report.

Thanks