statistics
posted by carrie .
The average age of evening students at a local college has been 21.
A sample of 19 students was selected in order to determine whether the average age of students had increased.
The average age of the students in the sample was 23 with a standard deviation of 3.5. Determine whether or not there has been an increase in the average age of the evening students. Use a 0.1 level of significance.

Do you want P = 0.1 or .01?
Z = (mean1  mean2)/standard error (SE) of difference between means
SEdiff = √(SEmean1^2 + SEmean2^2)
SEm = SD/√(n1)
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.