However, when sample size is 7 or less, if we use normal probability plot to check for normality, we may fail to reject Normality due to not enough sample size. In the examples here in these lessons and in the textbook we typically use small sample sizes and this might be the wrong image to give you. These small samples have been set for illustration purposes only. When you have a sample size of 5 you really do not have enough power to say the distribution is a normal and we will use a nonparametric methods instead of t .