A standard measure of test anxiety is knnown to produce a u=19. In the sample you draw of 86 the mean is equal 17.5 with a standard deviation s=10.
a-Use a level of 0.05 to test the hypothesis that the mean is less than 19.
b-find the 95% one sample confidence interval for the mean.
What have you done with this problem? What is the null hypthesis and the alternative one? Do you know how to start the problem? How to get z here? Is it a two tailed test or a one tailed? Can I see a little of your work?
In mathematics, you don't understand things. You just get used to them.
Of course that result can be rigorously obtained, but who cares?
Combinatorics is Algebra and Algebra is Combinatorics.