It's believed that as many as 24% of adults over 50 never graduated from high school. We wish to see if this percentage is the same among the 25 to 30 age group. ) How many of this younger age group must we survey in order to estimate the proportion of non-grads to within 10% with 90% confidence? Suppose we want to cut the margin of error to 3%. What is the necessary sample size?
Added by Mohamed G.
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The formula is: n = (Z^2 * p * (1-p)) / E^2 where: n = sample size Z = Z-score (which corresponds to the desired confidence level) p = estimated proportion of the population E = desired margin of error Show more…
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It's believed that as many as $21 \%$ of adults over 50 never graduated from high school. We wish to see if this percentage is the same among the 25 to 30 age group. a) How many of this younger age group must we survey in order to estimate the proportion of non-grads to within $10 \%$ with $90 \%$ confidence? b) Suppose we want to cut the margin of error to $4 \%$. What's the necessary sample size? c) What sample size would produce a margin of error of 5\%?
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You wish to estimate, with $95 \%$ confidence, the population proportion of U.S. adults who say that chocolate is their favorite ice cream flavor. Your estimate must be accurate within $5 \%$ of the population proportion. (a) No preliminary estimate is available. Find the minimum sample size needed. (b) Find the minimum sample size needed, using a prior study that found that $28 \%$ of U.S. adults say that chocolate is their favorite ice cream flavor. (c) Compare the results from parts (a) and (b).
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