to estimate the confidence interval. We use Student’s tdistribution. To compare the Zdistribution with the tdistribution, it can be noted that when nbecomes larger, the tdistribution approaches the Zdistribution. The common practice is that we can use Zinstead of twhen nis greater than 120. Properties of the t-Distribution •Mean = 0 •Mound-shaped •Symmetric •When n becomes larger, tbecomes closer to Normal Distribution