A sample of 20 pieces of laminate used in the manufacture of circuit boards was
ID: 3223704 • Letter: A
Question
A sample of 20 pieces of laminate used in the manufacture of circuit boards was selected and the amount of warpage (in inches) under particular conditions was determined for each piece. The sample mean warpage was .0705 and the sample standard deviation was .0062.
(a) Calculate an interval for which you have a high degree of confidence that at least 95% of all pieces of laminate result in amounts of warpage between the two limits of the interval.
(b) Explain why your interval in part (a) is wider than a 95% confidence interval for µ would be.
Explanation / Answer
a) z value at 95% = 1.96
mean= 0.0705 , s = 0.0062 , n =20
CI = mean + / - z * (s / sqrt(n))
= 0.0705 + / -1.96 * ( 0.0062 / sqrt(20))
= (0.0678 , 0.0732)