D looks right. The sample mean has standard deviation 15/sqrt(25) = 3, so 54.5 is 1.5 standard deviations below the mean and 64.5 is 1.5 standard deviations above.Originally Posted by NICEKID
Is there a correct answer found in my choices. I could not find one.
A sample of 25 is taken from a population which has a normal distribution with a mean of 60 and standard deviation of 15. The probability that the sample mean is between 55.5 and 64.5 is?