Question

The accounting department at Weston Materials Inc., a national manufacturer of unattached garages, reports that it takes two construction workers a mean of 44 hours and a standard deviation of 5 hours to erect the Red Barn model. Assume the assembly times follow the normal distribution. Refer to the table in Appendix B.1. a-1. Determine the z-values for 38 and 47 hours. (Negative answers should be indicated by a minus sign. Round the final answers to 1 decimal place.) 38 hours corresponds to z = 47 hours corresponds to z = a-2. What percentage of the garages take between 44 hours and 47 hours to erect? (Round the final answer to 2 decimal places.) Percentage % b. What percentage of the garages take between 38 hours and 47 hours to erect? (Round the final answer to 2 decimal places.) Percentage % c. What percentage of the garages take 37.4 hours or less to erect? (Round the final answer to 2 decimal places.) Percentage % d. Of the garages, 8% take how many hours or more to erect? (Round the final answer to 1 decimal place.) Hours

Answer 1

a-1) 38 hours corresponds to z = (38-44)/5=-1.2

47 hours corresponds to z = (47-44)/5=0.6

a-2)

percentage of the garages take between 44 hours and 47 hours to erect =22.57%

b)percentage of the garages take between 38 hours and 47 hours to erec t=61.06% (try 61.07% if this comes wrong)

c)percentage of the garages take 37.4 hours or less to erect =9.34%

d)

for 92th percentile critical value of z=		1.41
therefore corresponding value=mean+z*std deviation=			51.1 Hours(try 51.0 if this comes wrong)