I would like to ask how to test if the subset is representative to the whole dataset. I have for example 150 values in whole "population" and I selected (not randomly) 30 of them. I would like to test if these 30 values are representative in central tendention parameters to the whole "population". What can I use? I was thinking about t-tests.. But is it correct that the whole "population" contains also those 30 values from the subset? Thank you very much in advance. I am appreciating any help.