Employees that work on the computer frequently are subject to work-related injuries. One disorder, caused by strains to the hands and wrists, is called carpal tunnel syndrome. It strikes as many as 23 000 workers per year. The Australian Labor Department estimates that the average cost of this disorder to employers and insurers is approximately $33 000 per injured worker. Assume these costs are normally distributed, with a standard deviation of $9000.
Required:
a) Determine the proportion of costs between $15 000 and $45 000.
b) Determine the proportion of costs that are greater than $50 000.
c) Determine the proportion of costs between $5 000 and $20 O0O.
d) Calculate the value of the standard deviation, assuming the standard deviation is unknown, but 90.82% of the costs are more than $7000.
e) Calculate the average cost of 79.95% of the costs were less than $33 000, assuming that the mean value is unknown but the standard deviation is still $9 000.