Hi everyone,
I am a PhD student.
I have been collecting samples for 1 year and a month. My sample size calculation is 20. I have collected more than 20 samples so far. I am wondering whether my sample size will be enough or not. Should I continue my samples collection or just stop at this time? I have lots more works to do in the lab to fulfill my other objectives.

Thanks in advance.

anyone???

You haven't said what your subject area is, what kind of experiment you are doing or what kind of sample you mean - perhaps with a bit more information, someone might be able to comment. If you did a reliable calculation that said you need 20 samples and you've exceeded that number, it sounds like you've done what you set out to do, but since you're doubting it, perhaps it is best to check with your supervisor?

I am doing a research on cancer. However it is very hard to get the samples for my research. Usually the samples will only be available once in a month if I was lucky. My research is mostly on microarray. I have already talked to the statistician and he said for my research, there is no sample size calculation. The only thing I have to do is to collect all samples available in one year to be included in my study.

I have talked to my supervisor but then he wanted to have more. Should I continue to collect more or try to convince him that my sample collection is enough?

Your field is very different to mine, but in your position, I would go on trying to get more samples if that is what your supervisor has advised, and since there is no reliable way to calculate how many are needed. It does sound a bit frustrating if it is progressing so slowly, but that is also the case in my study which is very different - I think it's a very common PhD experience to feel as if data collection is never-ending!

The only problem I have now is the person who is in charge to give me the samples is harassing me. He always yells at me and cannot tolerate even a tiny mistake I do like asking question if I don't understand anything. He's beyond useless. I want to tell my supervisor about this problem as this will definitely create unnecessary stress towards my studies but then thinking he's my supervisor's best friend, I don't go with the plan.

However I really don't need unnecessary stress right now. I need to finish my lab works as soon as possible and start writing my thesis. Should I tell my supervisor about this problem?

I've seen your other thread that you posted now, and it's clear that you're in a difficult situation. Is there an identified member of staff at your uni/department who is responsible for PhD students as a group? Or a student welfare service, student union rep etc? I would go to someone like that and talk about the problem, as it does sound like you need to get some support.

Yes. There is a support group in my campus that I can talk to. However I don't really think it will be reliable as far as talking about harassment is concerned. I am thinking to convince my supervisor that I have enough samples and just being quiet about this matter. It will be the best one since I don't want to cause any drama in the future.

If your uni has a counselling or student support service, it should be possible to talk to someone confidentially - this is something you can ask before talking to them. There may even be a telephone support service so you don't need to give any personal details.