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# How do you estimate the mean length of plastic sheets?

A machine cuts plastic into sheets that are 30 feet (360 inches) long. Assume that the population of lengths is normally distributed.

a) The company wants to estimate the mean length the machine is cutting the plastic within 0.25 inch. Determine the minimum sample size required to construct a 90% confidence interval or the population mean. Assume the population standard deviation is 0.50 inch.

N =______ round up to the nearest whole number as needed.

b) Repeat part (a) using an error tolerance o 0.125 inch.

N =______ round up to the nearest whole number as needed

Which error tolerance requires a larger sample size?

#### Solution Preview

A machine cuts plastic into sheets that are 30 feet (360 inches) long. Assume that the population o lengths is normally distributed.

a) The company wants to estimate the mean length the machine is cutting the plastic within 0.25 inch. ...

#### Solution Summary

The solution examines the mean and normal distribution. The error of tolerance required for a larger sample size is determined.

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