1) see the first attached image. The sample size should be 1814 for this example. I entered in the Power and clicked "Continue" and 302 was generated in the Sample Size box. 2.1) The source is linked: NCSS document table and I have attached the table I used as the second image below. The first 4 values are different. I also cannot speak to its validity, so when I saw that it disagreed with the JMP tool I found an online guide for an excel tool to check the numbers, which I replicated. The table and the excel functions got the same results, which differ from the JMP tool. 2.2) That make sense, but I don't understand why I am seeing different numbers for the same inputs. 2.3) For sample size 24 I calculate a power of .10510478. I put rounded values in the post above, but I use unrounded values in the calculation. I wonder if the excel function and the NCSS software use a a different number of digits from the JMP tool.
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Hi Mark, Thank you for this tool. I am using JMP 13.1.0 and have encountered a few issues with the add-in. 1) The calculated sample size appears to be capped at NMT 302. 2) I found a table online to check the tool against, and I was getting different values for sample size at low power level. For example at alpha=.01, std1=1.0, std2=0.7, power=0.1, Lower One-Sided, the add-in gives me a sample size of 26. But when I calculate this by hand, I get a sample size of 24. var1/var2 = 1.0^2/0.7^2 = 2.0408 F^-1 of .99 with df of 11 and 11 (assuming total N=24) is .2241 F of (2.0408 * .2241) with same dfs is .8949 Power would be .1051 Did I make a mistake? Is your tool using a different formula?
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