A researcher wishes to estimate, with 90% confidence, the population proportion of adults who eat fast food four to six times per week. Her estimate must be accurate
within 3% 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 the respondents said they eat fast food four to six times per week.
(c) Compare the results from parts (a) and (b).
(a) What is the minimum sample size needed assuming that no prior information is available?
(Round up to the nearest whole number as needed.)