Intent of Question
The primary goals of this question are to evaluate a student's ability to: (1) identify and compute an appropriate
confidence interval, after checking the necessary conditions; (2) interpret the interval in the context of the
question; and (3) use the confidence interval to conduct an appropriate test of significance.
Solution
Part (a):
Step 1: Identifies the appropriate confidence interval by name or formula and checks appropriate conditions.
Two sample z confidence interval for D N p - p , the difference in the proportions of parts meeting
specifications for the two shifts OR ( ) * ˆ ˆ ( ) 1 ˆ ˆ ( ) 1 ˆ ˆ D D N N
D N
D N
p p p p
p p z
n n
- - - ± + .
Conditions: 1. Independent random samples from two separate populations
