Sample Size kMeans: What is the " Difference in Means" measure?

Olaf

If I enter in k Means Sample Size Calculator two prospective Means for separation across groups e.g. 100 and 200 (and a Std. Dev of 25) the Power by Sample Size Curve lists a "Difference in Means" of 70,710678. 

I would have expected 100. What is "Difference in Means" used for?

Olaf

JMP 17, Mac

Could not find info using the "Help" Tool

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Mark_Bailey

First, you should use the calculator for the difference between two means. That calculator will present the results you expect.

 

 

You used the calculator for k means based on the Analysis of Variance, not a t-test of a simple difference. What if you had 8 means? The 'difference' is captured in the way the ANOVA will work. I attached a detailed explanation in a JMP technical report for you. See Section 2.3, which starts in the middle of page 5.

 

Second, JMP 17 introduced a whole new class of calculators that we think are superior to the older calculators, which will be deprecated in the future. You might take a look at them here and see what you think. Here is the sample size explorer for two means:

 

Power and Sample Size Calculators in JMP.pdf