Hi all,
I have two things that I would like to ask:

1) Say when I want to compute the average grade for one undergraduate course "Math" for students in a university, I would consider all these students to be my population, say I took ten students as a sample and I computed the average grade for the math course.

If I increased the number of samples say to 30 students, and I computed the average. Now, if somebody asked me why we try 10 or 30 what is the difference?
My answer to that question is that the more we increase the number of samples, the sharpner the results would be, in other words, we are reaching the true mean by increasing the number of samples, please confirm if this is the right answer.

2) What is oversampling? from my understanding, I am taking too many samples, but I am not sure.

Thank you