Question

Thompson and Thompson is a steel bolts manufacturing company. Their current steel bolts have a mean diameter of 149 millimeters, and a standard deviation of 5 millimeters.

If a random sample of 49 steel bolts is selected, what is the probability that the sample mean would be less than 150.4 millimeters? Round your answer to four decimal places.

Answer 1

Solution :

Given that ,

mean = = 149

standard deviation = = 5

n = 49

= 149

= / n = 5 / 49 = 0.7143

P( < 150.4) = P(( - ) / < (150.4 - 149) / 0.7143)

= P(z < 1.96)

= 0.9750

Probability = 0.9750