Probability
posted by John on .
7. The random variable X is distributed normally with a mean of 12.46 and variance of 13.11. You collect a random sample of size 37.
a. What is the probability that your sample mean is between 12 and 13?
b. What is the probability that a single observation is between 12 and 13?
c. What is the probability that all of your observations are between 12 and 13?

a. Z = (scoremean)/SEm
SEm = SD/√n
SD = √variance
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability related to the Z score.
b. Z = (scoremean)/SD
Use same table.
c. I'm not sure about this one.