For the graph to represent your data most effectively, consider the following guidelines.
The sample size should be approximately 10 or greater for each group
Usually, the larger the sample size, the smaller and more precise the confidence interval. If the confidence interval is too wide, try to collect a larger sample. If you have multiple Y variables, the sample size should be approximately 10 or greater for each Y variable.
Groups should have approximately the same sample size
Large differences in sample sizes between groups (or multiple Y variables) can affect the widths of the intervals, and may produce misleading results. If sample sizes for the groups (or multiple Y variables) are approximately the same, you can be more confident that differences in the widths of the intervals is primarily due to differences in variation.
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.
