Importing data into inference app

[mbeddo]

Tim,

I am teaching college statistics, using "Understanding Statistics in the Behavioral Sciences" by Robert Pagano. On page 106, two formulas for computing a z score from a raw score are presented - one for population data, and one for sample data. Only difference between the two is using sample vs population means/standard deviations.

If the inference app is going to allow you to import values from a list for a z test, then why it imports the sample mean and not the sample standard deviation is what I find puzzling. If the app is willing to use the sample mean as a measure of the population mean, then why not import the sample standard deviation as a measure of the population standard deviation, since according to the textbook a z-test for sample data is allowed?

The main requirement for a z-test to be valid is that the values come from a parent distribution that is normal. Ultimately, it is the practitioner that takes on the responsibility whether a z-test is even valid in the first place. There are plenty of problems in the chapter of that textbook with a lot less than 30 points, and the students are expected to play with z-scores and areas under the standard normal curve.

I guess I find the arbitrary "1/sqrt(12)" as a default standard deviation irritating. Please consider, when importing into the inference app, copying the sample standard deviations along with the sample means into the z-test setup screen.

Thanks.