We have two manufacturing processes, A and B, for making A36 steel. The expected yield strength for both processes are 36000 psi. We have found that process A has variance 100 psi^2 and process B has variance 144 psi^2.

a. If we draw 37 samples from A and 35 samples from B, what is the variance of the difference in the sample averages?

1. 12.00
2. 15.62
3. 6.82
4. 244.00
5. 10.00

b. If we draw 37 samples from A and 35 samples from B, what is the probability that the sample average from A is larger than the sample average from B?

1. 2.61
2. 0.69
3. 0.50
4 0.31

c. Is this probability calculation from an approximate or exact distribution?
1. exact
2. approximate