Samples and Populations

[prissyg]

Does a researcher define the POPULATION under study?
Why do sampling errors occur?
What happens when we increase the level of confidence from 95% to 99%?(is it that we lose precision but gain certainty that our answer is accurate?)

 

[tkhunny]

Does a researcher define the POPULATION under study?

I sincerely hope so.

Why do sampling errors occur?

A little vague. Do youmean the estimation error due to sampling or do you mean straight up getting the sample wrong?

What happens when we increase the level of confidence from 95% to 99%?(is it that we lose precision but gain certainty that our answer is accurate?)

I don't understand "lose precision" in this context. The interval is wider. Is that what you mean? Should we talk about Type I and Type II Error, here?