HP F2226A - 48GII Graphic Calculator User Manual page 601

The variable ∆µ represents µ 1 – µ2.
Example 3 – A survey of public opinion indicates that in a sample of 150
people 60 favor increasing property taxes to finance some public projects.
Determine the 99% confidence interval for the population proportion that
would favor increasing taxes.
Press ‚Ù—@@@OK@@@to access the confidence interval feature in the
calculator. Press ˜˜ @@@OK@@@ to select option 3. Z-INT: µ 1 – µ2.. Enter
the following values:
When done, press @@@OK@@@. The results, as text and graph, are shown below:
Example 4 -- Determine a 90% confidence interval for the difference between
two proportions if sample 1 shows 20 successes out of 120 trials, and sample
2 shows 15 successes out of 100 trials.
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