Answer:
Explanation:
(1)Suppose that 84% of a sample of 125 nurses working 7 AM to 3 PM shifts in city hospitals
express positive job satisfaction, while only 72% of a sample of 150 nurses on 11 PM to 7 AM
shifts express similar fulfillment. Establish a 90% confidence interval estimate for the difference
and interpret.
p1 – proportion of nurses working day shifts
p2 – proportion of nurses working night shifts
Conditions:
1. Random – assume samples are representative of the populations
2. Independence – it is safe to assume that the samples would be independent of each other
3. 10% Condition – 125 nurses is less than 10% of all nurses working a day shift. 150 nurses is
less than 10% of all nurses working a night shift.
4. Success/Failure -
1 1 2 2 n p n p
ˆ ˆ
105 10 108 10
1 1 2 2 n q n q
ˆ ˆ
20 10 42 10
All conditions have been met to use the Normal model for a 2 proportion z-interval.
CI:
1 2
1 1 2 2
1 2
1 2
105 108
ˆ ˆ 0.84 0.72
125 150
ˆ ˆ ˆ ˆ
( ) * ˆ ˆ
(0.84)(0.16) (0.72)(0.28) (0.84 0.72) 1.645
125 150
p p
p q p q
p p z
n n
CI: (0.0391, 0.2009)
We are 90% confident that the true proportion of nurses working a day shift who express positive
job satisfaction is between 3.9% to 20.1% higher than for nurses working a night shift.