Annually, our assessment office mails out a form requesting income and expense info from commercial property owners. About 40% respond. The data is analyzed in Excel. As you may know, Excel has two basic formats for calculating standard deviation - that for a sample and that for a population. My question is: does the body (or total) of responses constitute the 'population' of the responses? That is after all, all that we have received. Or is it a sample since not everyone responded? To me, a sample would be randomly selected responses from the population of returned surveys. I think I should use the population form of the standard deviation function. Thank you for your insight.