Chapter 10 Inference on Two Samples

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Chapter 10Inference on Two Samples

• 10.3
• Inference About Two Population Proportions

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Step 1. A claim is made regarding two population
proportions. The claim is used to determine the
null and alternative hypothesis. The hypothesis
can be structured in one of three ways.
NOTE p1 is the assumed value of the population
proportion for population 1 and p2 is the assumed
value of the population proportion for population
2.
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Step 4 Compare the critical value with the test
statistic
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Step 5 State the conclusion.
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EXAMPLE Finding a Confidence Interval for the
Difference between Two Population Proportions An
economist obtains a random sample of 800 urban
households and finds that 338 of them have
Internet access. He obtains a random sample of
750 rural households and finds that 292 of them
have Internet access. Find a 99 confidence
interval for the difference between the
proportion of urban households that have Internet
access and the proportion of rural households
that have Internet access.
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EXAMPLE Determining Sample Size A doctor wants
to estimate the difference in the proportion of
15 - 19 year old mothers that received prenatal
care and the proportion of 30 - 34 year old
mothers that received prenatal care. What sample
size should be obtained if she wishes the
estimate to be within 2 percentage points with
95 confidence assuming (a) she uses the results
of the National Vital Statistics Report results
in which 98.0 of 15-19 year old mothers received
prenatal care and 99.2 of 30-34 year old mothers
received prenatal care. (b) she does not use any
prior estimates.