Question

Specimens of a new insulation for cables will be tested under high-temperature stress condition in order to estimate the chance of failure under this stress. From experience with a similar material, the sustainability under the stress for both success and failure specimens are normally distributed.

a. A random sample of 40 specimens was tested and it was found that 27 had failed. Set up a 95% confidence interval estimate for the true probability of failure.

b. Suppose the investigator wants to reduce the width of the interval estimate obtained in part (a) by half and increase the confidence level to 99%. At least how many specimens should be needed to achieve this?

Answer 1

Solution-

Given data,

n= 40

x= 27