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The variable
∆µ
represents
µ
1 –
µ
2.
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 –
µ
2.. 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.