Suppose that the mean age of Mount Sac juniors is 20 years with a standard deviation of 5 years

Question

And, the mean age of CSUF juniors is 21 years with a standard deviation of 4. Also, assume that the population ages are normally distributed. Hint: the conditions are met to use the normal model - you don't need to check it for this question.

Suppose you take a random sample of 28 juniors from Mount Sac and 25 juniors from CSUF.

What is the mean of the sampling distribution of the difference in mean ages of Mount Sac and CSUF juniors, Mount Sac - CSUF?

  What is the standard deviation of the sampling distribution of the difference in mean ages of Mount Sac and CSUF juniors?

  

Draw out the normal model for this situation, between which 2 values whould you expect the middle 95% of all ages to be.(Hint: put the smaller number on the left.)

and

Answer 1

You are constructing a t distribution. The mean difference is -1. The pooled sd is 4.55. The se is 4.55/3.63=1.25. The spread is based on t and is 2.008*sd=2.51. Ci low = -1-2.51 ci upper = -1+2.51. As such (-3.51, -1.51).