For the graph to represent your data most effectively, consider the following guidelines.
The sample size should be greater than 20
If you are trying to visualize the fit of the distribution line to your data, a sample size of less than 20 may be difficult to evaluate.
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.
