In each part of given question, explain whether the proportion that is described is a sample proportion or a population proportion.
a. In the 1990 U.S. Census, it was found that about one in nine Americans were at least 65 years old at that time.
b. A randomly selected group of 500 registered voters in your state is asked whom they intend to vote for in an upcoming election for governor. Based on the proportion choosing each candidate, the polling organization predicts the election winner.
c. In a clinical trial done to assess the effectiveness of a new medication for asthma, a satisfactory relief from symptoms was experienced by 55% of n = 80 participants.