Question

The diameter of a brand of tennis balls is approximately normally distributed, with a mean of 2.73 inches and a standard deviation of 0.03 inch. A random sample of 12 tennis balls is selected. Complete parts (a) through (d) below

The probability is 69% that the sample mean will be between what two values symmetrically distributed around the population mean?

The lower bound is inches. The upper bound is inches

Answer 1

Let denotes the mean diameter of randomly selected sample of 12 tennis balls.

or

a) To find x₁ and x₂ such that

Now,

Similarly,

Lower bound = 2.7212

Upper bound = 2.7388