Question

The diameter of small Nerf balls manufactured at a factory in China is expected to be approximately normally distributed with a mean of 5.2 inches and a standard deviation of .08 inches. Suppose a random sample of 20 balls is selected. What percentage of sample means will be less than 5.14 inches?

.048

22.66

4.8

.00048

Answer 1

Solution :

Given that ,

mean = = 5.2

standard deviation = = 0.08

n = 20

= 5.2

= / n = 0.08 / 20 = 0.0179

P( < 5.14)

= P(( - ) / < (5.14 - 5.2) / 0.0179)

= P(z < -3.35)

Using z table

= 0.00048

Probability = 0.00048

Correct option :- 0.00048