Here are links to practice problems that are among the topics for the second exam. The questions are at the bottom of each lost and the answers are in the comments.
Confidence of victory
Confidence intervals for proportions
More confidence intervals for proportions
What percentage of American women are listed as a given height?
Confidence intervals for averages of numerical data and two tests for normally distributed data
Confidence intervals for standard deviation of numerical data
More confidence intervals for averages and tests for normal distribution
z-scores and percentages above and below a given z-score in a normally distributed set
Practice for finding n given a margin of error.
If we have taken p-hat in a previous sample and it was 42%, what is the minimum n we should poll to get a margin of error of no more than 2.3%?
If we haven't taken a previous poll, what is the minimum n we should take to get a margin of error of no more than 2.3%?
Answers in the comments.
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1 comment:
We can use .42 and .58 for p-hat and q-hat in our formula, and that gives us
n >= 1.96^2*.58*.42/.023^2 = 1769.024...,
so n >= 1770.
If we have taken no poll, we have to assume p-hat = q-hat = .50.
n >= 1.96^2*.50*.50/.023^2 = 1815.024...,
so n >= 1816.
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