Statistics
posted by Jason L .
A building contractor claims that they can renovate a 200 sq foot kitchen and dining room in 40 work hours plus minus 5 (the mean and standard deviation respectively). The work includes plumbing, electrical installation, cabinets, flooring, painting and installing new appliances. From past experience we assume that times to complete similar projects are normally distributed. In order to gain a competitive edge the contractor wishes to guarentee a completion date. If the job is not done in a specified number of hours the contracter will reimburse 20% of the total cost to the owner. What should the number of hours be if they wish to take no more than a 6% risk of having to pay up? Advice  Draw the key elements of the solution before you compute.
You can use zscores and the zscore formula to compute the number of hours.
Formula: z = (x  mean)/sd >sd = standard deviation
You are given the mean and standard deviation. You can find z using a ztable representing "no more than 6% risk" of having to pay up. Once you have that zscore, all you will need to do is solve the above equation for x.
I hope this will help get you started.
Respond to this Question
Similar Questions

Statistics
A building contractor claims that they can renovate a 200 sq foot kitchen and dining room in 40 work hours plus minus 5 (the mean and standard deviation respectively). The work includes plumbing, electrical installation, cabinets, … 
statistics
Assume we draw a simple random sample from a population having a mean of 100 and a standard deviation of 16. What is the probability that a sample mean will be within plusorminus two of the population mean for each of the following … 
statistic
Let's assume there are 3 people in Room A and another 3 people in Room B. The ages of the people in Room A are 25, 25, and 25. The ages of the people in Room B are: 10, 25, and 40. The mean of the ages in both rooms is 25. Does that … 
statistics/mean and standard deviation
find the mean and standard deviation in the following probability distribution x 1 2 3 p(x) 0.2 0.6 0.2 *i think that the mean is 2 but am lost after that when it comes to the standard deviation. please show work and calculations. … 
math
A carpeted living room and dining room area measures 32 ft by 10 ft. Mark decides to install wood flooring in the 12 ft by 10 ft dining room. By what percent has he reduced the area that is carpeted? 
Math
Suppose you want to use hardwood flooring for most of a 750 square foot apartment. Labor costs are $250 plus a $2 feet per square foot of installation. The cost per square foot of hardwood flooring is $7.00. Write an inequality to … 
Statistics
In an advertisement, a shoe store claims that its mean online delivery time is less than 30 hours. A random selection of 36 delivery times has a sample mean of 28.5 hours and a standard deviation of 3.5 hours. 
statistics
Let's pretend the Work variable is normally distributed, with a mean/median/mode value of 22 and a standard deviation of 17. Based on these numbers, we can say that approximately 50 percent of SOC 390 students work more than ____ hours … 
statistics
The mean length of a work week for the population of workers was reported to be 39.2 hours. Suppose that we would like to take a current sample of workers to see whether the mean length of a work week has changed from the previously … 
math
Here's my question: Determine if each system has one, two, or no solutions. (Show your work  3 marks each) a)y=2x^22x+1 and y=3x5 b)y=x^2+3x16 and y=x^28x18 Here's my work on the question: a) x=(b plus/minus sign (square root …