CHAPTER 10B
8
CENGAGE
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Interval Estimation of \( \boldsymbol{p}_{\mathbf{1}}-\boldsymbol{p}_{\mathbf{2}} \) (3 of 5)
Example: Tax preparation firm
Independent random samples from the two offices provide the following information:
Office 1
\( n_{1}=250 \)
Number of returns with errors \( =35 \)
Office 2
\( n_{2}=300 \)
Number of returns with errors \( =27 \)
CENGAGE
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Point Estimator of the Difference between Two Population Proportions
Example: Tax preparation firm
\( p_{1}= \) proportion of erroneous returns for population 1 (office 1)
\( p_{2}= \) proportion of erroneous returns for population 2 (office 2)
\( \bar{p}_{1}= \) sample proportion for a random sample from population 1
\( \bar{p}_{2}= \) sample proportion for a random sample from population 2
\[
\bar{p}_{1}-\bar{p}_{2}=\frac{35}{250}-\frac{27}{300}=.14-.09=.05
\]
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Interval Estimation of \( p_{1}-p_{2} \) (4 of 5)