Question

Thompson and Thompson is a steel bolt manufacturing company. Their current steel bolts has a mean diameter of 140 mm and a variance of 36. If a random sample of 50 steel bolt is selected what is the probability that the sample mean would be greater than 142.5 mm round your answer to four decimal places

Answer 1

Solution :

Given that ,

mean = = 140

standard deviation = = 6

= / n = 6 / 50 = 0.8485

P( > 142.5) = 1 - P( < 142.5)

= 1 - P[( - ) / < (142.5 - 140) / 0.8485]

= 1 - P(z < 2.95)

= 0.0016

Probability = 0.0016