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What does the Tukey Kramer test show?
The test is known by several different names. Tukey’s test compares the means of all treatments to the mean of every other treatment and is considered the best available method in cases when confidence intervals are desired or if sample sizes are unequal (Wikipedia).
What are pairwise confidence intervals?
In the pairwise comparison of the group means, many confidence intervals are formed. For example, when there are three groups, we form confidence intervals for the differences of groups 1 and 2, groups 1 and 3, and groups 2 and 3. When there are r groups, there are rC2 confidence intervals for the pairwise comparisons.
How to interpret a Tukey-Kramer confidence interval?
On the y-axis you have all the tested contrasts, that is 2 vs 1, 3 vs 1, 4 vs 2. On the x-axis you have the mean differences (the points) for that particular contrast. The lines represent the 95 % confidence interval.
Which is an example of the Tukey Kramer test?
Example 1: Analyze the data in range A3:D15 of Figure 1 using the Tukey-Kramer test to compare the population means of women taking the drug and the control group taking the placebo. This example is the same as Example 1 of Tukey HSD but with some data missing, and so there are unequal sample sizes.
What does the x-axis mean in Tukey Kramer?
The x-axis represent the mean differences that were found between those pairs. So for example the comparison 2-1 had a mean difference of 20. The extended lines show the 95% confidence intervals. In this case if the confidence interval crosses the 0 point – the difference would not be statistically significant.
What is the reference line at 0 in Tukey?
Comparison of 95% confidence intervals to the wider 99.35% confidence intervals used by Tukey’s in the previous example. The reference line at 0 shows how the wider Tukey confidence intervals can change your conclusions. Confidence intervals that contain zero indicate no difference.