Testing a claim using confidence levels.

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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... The margin of error is then given by e = z S/Sqrt(n). However, since 0< p <1, the actual confidence interval for p will be [max(0, p - e), min(1,p+e)]
<br>Since From the table we can find that Z=2.58
<br>* ...