PCC Incomes Worksheet

Exercises

A)As part of its quality assurance program, the Autolite Battery Company conducts tests on battery life. For a particular D-cell alkaline battery, the mean life is 19 hours. The useful life of the battery follows a normal distribution with a standard deviation of 1.2 hours. Answer the following questions.

1. About 68% of the batteries failed between what two values?
2. About 95% of the batteries failed between what two values?
3. About 99.7% of the batteries failed between what two values?

B) The distribution of the annual incomes of a group of middle-management employees at Compton Plastics approximates a normal distribution with a mean of $47,200 and a standard deviation of $800.

1. About 68% of the incomes lie between what two amounts?
2. About 95% of the incomes lie between what two amounts?
3. About 99.7% of of the incomes lie between what two amounts?
4. What are the median and the modal incomes?

C) A recent report in Pasadena Times indicated a typical family of four spends $490 per month on food. Assume the distribution of food expenditures for a family follows the normal distribution, with a standard deviation of $90 per month.

1. 1. What percent of the families spend between $300 and $490 per month on food?
   2. What is the probability that a families selected spends less than $430 per month on food?
   3. What percent spend between $430 and $600 per month on food?
   4. What is the probability of selecting a family that spends between $400 and $600 per month on food?