When should post hoc tests be used in data analysis?

Post hoc tests should be used after an ANOVA indicates significant differences among group means. This is because ANOVA (Analysis of Variance) is used to determine whether there are any statistically significant differences between the means of three or more independent groups. However, ANOVA does not specify which specific groups are different from each other; it only tells us that at least one group mean is significantly different from the others.

Once ANOVA shows significant results, post hoc tests can be conducted to identify specifically which group means are different. These tests control for the Type I error rate that increases when multiple comparisons are made and provide a more detailed understanding of the differences between groups. Therefore, the correct application of post hoc tests follows a significant ANOVA result, making the answer accurate.

Other options presented do not correctly describe the appropriate timing or context for the use of post hoc tests, as they either suggest scenarios that are unrelated to the need for post hoc comparisons or propose incorrect sequencing in the analysis process.