# Confidence Interval and Validity: Malfunctioning Processor

A computer store claimed that about 80% of all service calls are due to a malfunctioning processor. A sample of 100 service calls is randomly selected and it is found that 70 are due to malfunctioning of processors. Determine the 99% confidence interval for the true proportion of all service calls that are due to the malfunctioning of processors. Based upon the confidence interval that you constructed, what would you say about the validity of the stores claim?

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#### Solution Preview

In this case the sample probability is 70/100=0.7

<br>The sample deviation is given by S = Sqrt[(p)(1 - p)]; and e is the 99% margin of error. And z is the value such that P(-z <Z<z) = 0.99, where Z ~ ...

#### Solution Summary

A computer store claimed that about 80% of all service calls are due to a malfunctioning processor. A sample of 100 service calls is randomly selected and it is found that 70 are due to malfunctioning of processors. Determine the 99% confidence interval for the true proportion of all service calls that are due to the malfunctioning of processors. Based upon the confidence interval that you constructed, what would you say about the validity of the stores claim?