For the graph to represent your data most effectively, consider the following guidelines.
Collect summary data or raw data
You can create the chart with summarized data or raw data. For summarized data, each observation summarizes a category. Summarized data can be a count or a calculated value, such as a mean. For raw data, each observation is an occurrence or a defect. All the raw data are in one column of the worksheet, with each observation in a separate row.
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.
