I have a list of every store chain in the US with at least 100 locations in the US. a) What number of those do I have to pick in order to have a representative sample of the number of locations across the country or in a specific location? b) What number do we pick to have reasonable confidence that we have a representative sample of the number of locations in the US, if we do not know how many chains exist overall?
I am trying to identify the sample size based on the confidence level and that is what I have done so far: I selected a random number for the data sample size: let's say n= 100, 50, or 25. I derived confidence level based on that sample size and the confidence levels I have been getting were almost the same, So is there other way to approach this?
Any information would be helpful!