Data considerations for Normality Test

To ensure that your results are valid, consider the following guidelines when you collect data, perform the analysis, and interpret your results.

The data must be numeric: You must have numeric data, such as the weights of packages.
The sample data should be selected randomly: In statistics, random samples are used to make generalizations, or inferences, about a population. If your data are not collected randomly, your results may not represent the population. For more information, go to Randomness in samples of data.
The sample size should be greater than 20: A sample size that is less than 20 may not provide enough power to detect significant differences between your sample data and the normal distribution. However, use caution with very large sample sizes, as they may provide too much power. When a test has too much power, small and possibly meaningless differences between your sample data and the theoretical distribution appear to be significant.