Description:
This graph presents an example of a multiple comparisons plot. The boxplots and the pairwise comparison annotations were generated automatically by a one-way ANOVA, which produced a grouped boxplot for all six feed groups. The letters above each box indicate the significance of the differences among groups: groups sharing the same letter are not significantly different, while groups with different letters differ significantly.
Background:
Chick weight was measured in six groups fed with different feed types. Because the overall difference among the six groups was assessed by a standard one-way ANOVA, followed by multiple comparisons in which every pair of groups was compared using the Tukey HSD test at the 0.05 significance level. The results showed that chicks fed with casein and sunflower reached the highest weights (marked a), which were significantly higher than all other feeds, whereas horsebean yielded the lowest weight (marked c), significantly lower than every other group (***, p < 0.05).