Question

When should you run post hoc tests?

Why would you conduct a post hoc test?

Explain why not just run three different t-Tests, one comparing groups 1 and 2, one comparing groups 1 and 3, and one comparing groups 2 and 3?

Provide an example in which you would need to run a post-hoc test.

Answer 1

Post-hoc (Latin, signifying "after this") way to dissect the consequences of your test information. They are frequently in light of a familywise error rate; the likelihood of no less than one Type I error in a set (family) of comparisons. The most well-known post-hoc tests are:

Bonferroni Procedure

Duncan's new multiple range test (MRT)

Dunn's Multiple Comparison Test

Fisher's Least Significant Difference (LSD)

Holm-Bonferroni Procedure

Newman-Keuls

Rodger's Method

By and by, post hoc investigations are normally worried about discovering designs as well as relationships between subgroups of sampled populations that would some way or another stay undetected and unfamiliar were an academic group to depend entirely upon from the earlier statistical methods. Post hoc tests—otherwise called a posteriori tests—significantly extend the range and capacity of methods that can be connected in exploratory research. Post hoc examination reinforces acceptance by constraining the likelihood that critical impacts will appear to have been found between subgroups of a population when none really exist. As it may be, numerous logical papers are distributed without sufficient, protection post hoc control of the type I error rate.

Post hoc analysis is a vital procedure without which multivariate theory testing would enormously endure, rendering the odds of finding false positives inadmissibly high. At last, post hoc testing makes better educated researchers who can accordingly figure better, more effective from the earlier speculations and research plans.

Example: Newman– Keuls method
A stepwise multiple comparisons procedure used to recognize sample implies that are altogether not quite the same as each other. It is utilized regularly as a post hoc test at whatever point a huge difference between at least three sample implies has been uncovered by an analysis of variance (ANOVA)