I have a data-set for which I am not sure whether to look at the population standard deviation or the sample standard deviation. I have a group of 7 mice from which blood samples were collected at different time points (1 month, 2 month, 3 month etc). I want to find the standard deviation at each time point (so, the sd at 1 month, 2 months, and so forth). Since my sample size is not big, would I use the sample sd in this occasion? I am not quite sure which one would be appropriate for my experiment? Any input is greatly appreciated! Thank you!
Are you doing a scientific study on seven mice, or are you doing it on mice in general and are using seven of them as examples?
If it's the former, use the population SD, if it's the latter, use the sample SD. I suspect you are researching mice in general, so it'd be the sample SD I'd recommend.
Also, check what standard deviation your program uses as its default. Most software uses the sample standard deviation rather than the population standard deviation. I have been caught out by this before.