The margin of error formula is an equation that measures the range of values above and below the sample statistic. It is defined by taking the critical value and multiplying it by the standard error of the statistic.

The margin of error is inversely related to the square root of the sample size. The larger the sample (for example, of a population being surveyed), the smaller the margin of error. However, this formula does not rely on the size of the population. This formula is used to ensure that statistics of the sample population reflect the true outcome of a normal population a defined percentage of the time.