Normal Distribution Worksheet [TimeWeb]

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WORKSHEET

Normal Distribution

Before doing this worksheet, you should make sure that you know all about normal distributions. There is an explanation of the normal distribution curve in the explanation section.

Q1. Your firm has a contract to make one thousand staff uniforms for a fast-food retailer. The heights of the staff are normally distributed, with a mean of 69 inches and a standard deviation of 2 inches. What percentage of the uniforms will have to fit staff shorter than 67 inches? What percentage will have to be suitable for staff taller than 73 inches?
(Select one answer)

(a)

16% and 2.5%.

(b)

68% and 95%

(c)

32% and 5%.

Q2. Assuming that the results from all large tests are normally distributed. In the final results for Economics the mean percentage score is 80 with a standard deviation of 5%. In Business Studies the mean score is 70 with a standard deviation of 2.5%. You score 75% in both subjects. What percentage of students got better results than you in Economics and Business Studies?
(Select one answer)

(a)

84% of students score more than you in Economics. 2.5% score more in Business Studies.

(b)

16% in Economics and 2.5% in Business Studies.

(c)

68% in Economics and 95% in Business Studies.

Q3. The duration times of Dynamo batteries are normally distributed, with a mean of 80 hours and a standard deviation of 10 hours. As a marketing gimmick, the manufacturer offers a guarantee to replace any battery that fails prior to a certain time. Approximately how long a guarantee should Dynamo give, so that no more than 2.5 % of the batteries fail prior to the guaranteed time?
(Select one answer)

(a)

60 hours.

(b)

100 hours.

(c)

20 hours.

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