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.(c) Compare the results from parts (a) and (b).