The EPA considers indoor radon levels above 4 picocuries per liter (pCi/L) of air to be high enough to warrant amelioration efforts. Tests in a sample of 200 Centre County Pennsylvania homes found 127 of these sampled households to have indoor radon levels above 4 pCi/L.

a. Clearly define the population parameter being estimated by this sample data. (1pt)

b. What is a point estimation for this population parameter? (2pt)

c. What is the Margin of Error (ME) of estimation for this population parameter? Use 90%. Clearly write the formula and show work how you compute it.