Slovin's formula is written as n = N/(1+Ne^2). In the formula, n = the number of samples needed, N = total population and e = error tolerance.
Slovin's formula is used in statistical analysis as a tool to determine the sample size of a population that must be taken for a specific study. This formula is only used when the sample size is unknown; for example, since things like IQ scores tend to follow a predictable distribution pattern, it is easy to find an appropriate sample size for studying this topic. Using the formula, statisticians can come up with a reliable sample size to study a given population without having to study the entire population individually.