Robin said:And you would expect it to be 50%, but try this - generate 200 random numbers in a spreadsheet and then calculate the z scores using the assumed mean and standard deviation (as GCP does). Then calculate the percentage of positive z scores and try hitting the recalculate key a few times. This will vary from about 45% to 60% so the results are not unusual for purely random data.
Feel free to post a link to your Excel file, or to the code you use for each column.
I agree that it would vary approximately over that range, and that is in fact what yields such a small p-value, because it is unlikely to be that far out.
