Question

Thompson and Thompson is a steel bolts manufacturing company. Their current steel bolts have a mean diameter of 148 millimeters, and a standard deviation of 7 millimeters.

If a random sample of 31 steel bolts is selected, what is the probability that the sample mean would be less than 147.7 millimeters? Round your answer to four decimal places.

Answer 1

Solution :

Given that ,

mean = = 148

standard deviation = = 7

= / n = 7 / 31 = 1.2572

P( < 147.7) = P(( - ) / < (147.7 - 148) / 1.2572)

= P(z < -0.24)

= 0.4052

Probability = 0.4052