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1)A study of a long-distance phone calls made from General Electric Corporate Headquarters in Fairfield, Connecticut, revealed the length of calls, in minutes, follows the normal probability distribution

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1)A study of a long-distance phone calls made from General Electric Corporate Headquarters in Fairfield, Connecticut, revealed the length of calls, in minutes, follows the normal probability distribution. The mean length of time per call was 4.2 minutes and the standard deviation was 0.60 minute.

1. What fraction of the calls lasts between 4.2 and 5 minutes?
2. What fraction of the calls lasts more than 5 minutes?
3. What fraction of the calls lasts between 5 and 6 minutes?
4. What fraction of the calls lasts between 4 and 6 minutes?
5. As part of her report to the president, the director of communications would like to report the length of the longest (in duration) 4% of the calls, what is this time?

 

 

 

 

 

 

 

 

 

 

 

 

2.  Shaver Manufacturing Inc. offers dental insurance to its employees. A recent study by the human resource director shows the annual cost per employee per year followed the normal probability distribution, with a mean of $ 1,280 and a standard deviation of $ 420 per year.

1. What fraction of the employees cost more than $1,500 per year for dental expenses?
2. What fraction of the employees cost between $1,500 and $2000 per year?
3. Estimate the percent that did not have any dental expense?
4. What was the cost for the 10% of employees who incurred the highest dental expense?

 

 

 

 

 

 

 

 

3. According to the South Dakota Department of Health, the number of hours of TV viewing per week is higher among adult women than adult men. A recent study showed women spent an average of 34 hours per week watching TV, and men, 29 hours per week. Assume that the distribution of hours watched follows the normal distribution for both groups, and that the standard deviation among the women is 4.5 hours and is 5.1 hours for the men.

1. What percent of the women watch TV less than 40 hours per week?
2. What percent of the men watch TV more than 25 hours per week?
3. How many hours of TV do the 1% of women who watch the most TV per week watch? Find the comparable value for the men.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

4. Best Electronic Inc. offers a “no hassle” return policy. The number of items returned per day follows the normal probability distribution. The mean number of customer return is 10.3 per day and the standard deviation is 2.25 per day.

1. In what percent of the days are there eight or fewer customers returning items?
2. In what percent of the days are between 12 and 14 customer return items?
3. Is there any chance of a day with no return?