Answer:
The sample size required is 865.
Step-by-step explanation:
The (1 - <em>α</em>)% confidence interval for population mean is:
The margin of error of this interval is:
It is provided that all values of breakdown voltage are between 40 and 70.
So, the minimum value of breakdown voltage is, Min. = 40 and the maximum value of breakdown voltage is, Max. = 70.
Assume that the population standard of the distribution of breakdown voltage is known.
The standard deviation is:
The margin of error is, MOE = 1 kV.
The critical value of <em>z</em> for 95% confidence level is:
Compute the sample size as follows:
Thus, the sample size required is 865.