Do we have to undertake pilot study to calculate sample size and based on this study we have to calculate the sample size and then decide what should be our sample size for Phd thesis work.Please advice me in detail on this
If little is known about what kind of data to expect then it is a good idea to do a pilot study first. Sometimes expected values can be taken from published research if others have studied the same or similar topics. You should plan what kind of data you will get and the type of analysis you want to run and then do a power and sample size calculation.