A major transportation company operates a fleet of trucks and it claims that the mean monthly maintenance
Question:
A major transportation company operates a fleet of trucks and it claims that the mean monthly maintenance cost per truck is different from $80. To test this hypothesis, a random sample of 20 trucks provided a sample mean maintenance cost of $74 with a sample standard deviation of $10. Assume that the monthly maintenance cost per truck is normally distributed.
a. At a 2% level of significance, is there sufficient evidence to support the company’s claim?
b. The manager is also interested in estimating the percentage of imported trucks in the current fleet. A sample of 40 trucks revealed 5 were imported. At a 5% level of significance, is there evidence that the true proportion of imported trucks exceeds 10%?
c. To learn the work satisfaction of her drivers, the manager also wishes to estimate proportion of truck drivers satisfied with their work within 10% of the true value 9 times out of 10. Determine the number of truck drivers that would have to be sampled.
Elementary Statistics Picturing the World
ISBN: 978-0321911216
6th edition
Authors: Ron Larson, Betsy Farber