For the graph to represent your data most effectively, consider the following guidelines.
- The sample size should be between 20 and 1000
- 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. A sample size that is greater than 1000 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.
- The sample data should be selected randomly
- In statistics, random samples are used to make generalizations, or inferences, about a population. If your data were not collected randomly, your results may not represent the population.