Roger has read a report that the weights of adult mail Siberian tigers have a distribution which is approximately normal with mean μ = 390 lb and σ = 65 lb.
a) Find the probability that an individual male Siberian tiger will weigh more than 450 lb.
b Find the probability that a random sample of 4 male Siberian tigers will have a sample mean weight more than 450 lb.

Take a look at our examples section. There is a post on the normal distribution. a and b are almost the same question, except that in b you will divide by (s/sqrt(n)) because it involves the sampling distribution of average weights, not individual weights.