In teaching my classes, I've always stressed that under the usual assumptions with variance unknown, the t-test is appropriate and should always be used; however, a student recently posed a question which I could not answer. If doing a C.I. on proportions you don't know p, then you also don't know the variance. The question the students asked was Why don't we use the t-value when we form a C.I. on a proportion?
There is a great deal of logic to their question since clearly p is not normal. Anyone with any ideas?
----- End of forwarded message from Rudy Wiegand -----
I don't know. The text I use (Siegel) DOES use the t-distribution.
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