Contents
What is the null hypothesis for a Tukey test?
Tukey’s HSD is a multiple comparison technique that tests the null hypothesis that two means are equal. It should be used when you reject ANOVA’s omnibus null hypothesis AND the number of levels of the IV is greater than 2.
What is Tukey’s rule?
Tukey’s rule says that the outliers are values more than 1.5 times the interquartile range from the quartiles — either below Q1 − 1.5IQR, or above Q3 + 1.5IQR. outlier, and will take in a data vector, and return a Boolean vector, TRUE for the outlier observations and FALSE elsewhere.
What if my ANOVA is not significant?
If your one-way ANOVA p-value is less than your significance level, you know that some of the group means are different, but not which pairs of groups. Confidence intervals that do not contain zero indicate a mean difference that is statistically significant.
Is t-test same as Tukey?
The test statistic Tukey’s test is based on a formula very similar to that of the t-test. In fact, Tukey’s test is essentially a t-test, except that it corrects for family-wise error rate.
Why are post hoc tests needed for ANOVA but not for Z or T tests?
When the ANOVA is significant, post hoc tests are used to see differences between specific groups. post hoc tests control the family-wise error rate (inflated type I error rate) due to multiple comparisons. t-test does not control the inflated type I error rate.
How to get ANOVA results to match post hoc Tukey test?
I used SPSS and I used to have the same problem and I have tried different tests in the PostHoc. For equal variance assumed, I suggest you use Dunnet test in which you can have different results if you change the selection in Control category (First or Last) and sometimes in the Test (2-sided, < Control, > Control).
Why are there differences between ANOVA and no significance?
There has been some discussion about why differences exist between factor significance after an ANOVA and no significance in the pairwise comparisons, and it has been very helpful. However, there is no directions regarding how to proceed.
When to use ANOVA to test pattern of data?
You do an ANOVA to test the pattern of your data. If the test is passed then, in most situations, all you need to do is then describe that pattern. I used SPSS and I used to have the same problem and I have tried different tests in the PostHoc.