A social worker wants to know the proportion of the U.S. population over age 16 who provide eldercare - unpaid care for someone with a condition related to aging - to others. What size sample should be obtained if the social worker wants an estimate within 3 percentage points of the true proportion with 95% confidence if: a) The social worker uses the 2015 estimate from the American Time Use Survey of 16%. (5 points) b) The social worker does not use any prior estimates? (5 points)