For the graph to represent your data most effectively, consider the following guidelines.
Although there are no formal guidelines for the amount of data needed for a scatterplot, larger samples more clearly indicate patterns in the data. A scatterplot that has a fitted regression line is most effective when the sample size is approximately 40 or greater. If the sample size is less than 40, the fitted regression line may not be as accurate.
Usually, you should record the data in the worksheet in the same order that you collect it. Then, you can evaluate time-related patterns in the data.