High Resolution Graphics

What graphics best emphasize group differences or are useful to scan for outliers or unusual distributions?

• Dot Plots (the default) to assess within-group distributions, possible outlier and equality of variances. A red star marks each group mean.
• Box plots display each within-group median, P₂₅ and P₇₅, and special symbols denote outliers. Compare the median with the mean (it’s marked).
• Bar charts feature group means with standard errors and are often used in final reports
• Stacked histograms to assess how distributions change across ordered categories
• Bar charts of cell counts to check the sample size “balance”

The graphs can be displayed with or without within-group statistics – mean, standard deviation, standard error, minimum and maximum values and sample size.

Graphics with 7D, Analysis of Variance (ANOVA) with Data Screening

• Click on Image to Enlarge

Data are yearly income in US dollars from a small community grouped by level of education—high school dropout, high school graduate, some college, and college graduate.