For the graph to represent your data most effectively, consider the following guidelines.
The sample size should be medium to large
Although there are no formal guidelines for the amount of data needed for a scatterplot, larger samples more clearly indicate patterns in the data.
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.
