Deciding between Z Test and T-Test
So when we should perform the Z test and when we should perform t-Test? It’s a key question we need to answer if we want to master statistics.
If the sample size is large enough, then the Z test and t-Test will conclude with the same results. For a large sample size , Sample Variance will be a better estimate of Population variance so even if population variance is unknown, we can use the Z test using sample variance.
Similarly, for a Large Sample , we have a high degree of freedom. And since t -distribution approaches the normal distribution , t he difference between the z score and t score is negligible.