The half-width of a confidence interval is also referred to as amargin of error. Note that the half width is found by dividing thetotal length of the interval in half.

a) Before you collect data for inference on a populationprobability of success, you know you would like the margin of errorof the 95% confidence interval to be at most 3 percentage points.Use this information to determine the sample size needed for yourstudy. Use a prior value of p = .4 for this calculation.

b) Explain how your answer above would vary with your priorguess for the value of p.