Posted by sai on Friday, January 6, 2012 at 1:03pm.
You are conducting an experiment to see if a given therapy works to reduce test
anxiety in a sample of college students. A standard measure of test anxiety is known to
produce a = 19. In the sample you draw of 86 the mean is equal 17.5 with standard
deviation s = 10.
a Use an level of 0.05 to test the hypothesis that the mean is less than 19.
b Find the 95 % one sample con dence interval for the mean.

statistics  PsyDAG, Sunday, January 8, 2012 at 12:59pm
Z = (mean1  mean2)/standard error (SE) of difference between means
SEdiff = √(SEmean1^2 + SEmean2^2)
SEm = SD/√n
If only one SD is provided, you can use just that to determine SEdiff.
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score. Remember that your hypothesis leads to a onetailed test.
95% = mean ± 1.96 SEm