13. A researcher wishes to estimate, with 95%
confidence, the population proportion of adults who think Congress
is doing a good or excellent job. Her estimate must be accurate
within 2% of the true 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 40% of the respondents said they think
Congress is doing a good or excellent job.
14. A researcher wishes to estimate, with 95%
confidence, the population proportion of adults who support
labeling legislation for genetically modified
organisms (GMOs). Her estimate must be accurate within 6% of
the true 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 72% of the respondents said they support
labeling legislation for GMOs.