Is Your Data Normal? The Anderson-Darling Test
Have a look at the Excel Histogram chart above based on a given set of data. Does it look normally distributed? How could you find out? Well, you could calculate the kurtosis and skewness, e.g. using Descriptive Statistics , or generate a BoxPlot. But still, how can you know with certainty? Descriptive Statistics showing Kurtosis and Skewness BoxPlot of Sample Data Why is Checking for Normality Important? In previous blogs on One Sample Mean Test and Two Sample Mean Test , I assumed the given data is normally distributed. If the sample is normally distributed then choosing a parametric test like t-test is applicable since we are using the mean (central tendency) and standard deviation (spread) to calculate the t-statistics . Assuming normal distribution is a simplification. It is therefore only to justify using parametric tests. However, mean and standard deviation should not be used to describe a sample that is not normally distr