The time to occurrence of coronary artery disease in Iowa is heavily right skewed witha mean of 45 and standard deviation of 16. A random cohort of 64 Iowans has been selected and followed till the occurrence of coronary artery disease. Calculate the approximate probability thatthe sample mean time that coronary artery disease occurs is beyond 47 years.

The probabilities only apply to normal distributions. We do not know the degree of skew in the distribution.