- Find the required sample size for a desired margin of error and population’s confidence interval.
Is my sample big enough?
We encounter a variety of statistics on a daily basis. Journalists report polling data on upcoming elections, advertisers tell us how many people prefer their products over competitors, and healthcare researchers tell us the prevalence of a given disease across the country. Responsible researchers remind us that these reported statistics fall within a margin of error, but the size of that margin can vary greatly from study to study.
Recall that we can calculate the minimum sample size necessary for a study if we know the desired confidence level, the acceptable margin of error, and the population proportion. (Alternately, we can take a conservative approach and use [latex]0.5[/latex] for the proportion.)