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Construct and interpret a 95%confidence interval for p1-p2 in Exercise 24. Explain what additional information the confidence interval provides.

Short Answer

Expert verified

We are 95%confident that the proportion difference is between 0.0175 and 0.3075.

Step by step solution

01

Given Information

Given

x1=34

n1=80

x2=21

n2=80

02

Explanation

The sample proportion is the number of successes divided by the sample size:

p^1=x1n1=3480=0.425

p^2=x2n2=2180=0.2625

For confidence level 1-=0.95, determine z/2=z0.025using table II (look up 0.025in the table, the z-score is then the found z-score with opposite sign):

z/2=1.96

The endpoints of the confidence interval for p1-p2are then:

localid="1650451236001" p^1-p^2-z/2p^11-p^1n1+p^21-p^2n2=(0.425-0.2625)-1.960.425(1-0.425)80+0.2625(1-0.2625)800.0175

localid="1650451247912" p^1-p^2+z/2p^11-p^1n1+p^21-p^2n2=(0.425-0.2625)+1.960.425(1-0.425)80+0.2625(1-0.2625)800.3075

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