Question

3 Scenario 1 A quality control engineer is interested in the mean length of sheet insulation being cut automatically by machine. It is known that the standard deviation in the cutting length that this machine produces is 0.20 feet. A sample of 75 cut sheets yields a mean length of 12.25 feet. This sample will be used to obtain a confidence interval for the mean length cut by machine. Referring to Scenario 1, the 95% confidence interval goes from to 12.09 to 12.19 12.20 to 12.30 三鼎12.51 to 12.62 6.06 to 10.22

Answer 1

x̅ =12.25, σ =0.20, n =75

95% Confidence interval :

At α = 0.05, two tailed critical value, z crit = NORM.S.INV(0.05/ 2) = 1.960

Lower Bound = x̅ - z-crit*σ/√n = 12.20

Upper Bound = x̅ + z-crit*σ/√n = 12.30

Option 2nd.