A private polling organization conducts a national study on physical exercise. The reported responses for 1,507 individuals surveyed were as follows: 21.7% exercised daily, 39.1% exercised two to three times per week, 21.4% exercised four to six times per week, and 17.8% reported being sedentary.

(a) Are these numbers statistics or parameters? Explain.

(b) A method from this text predicts that the percentage of the entire national population that is sedentary is at least 12% but no greater than 18%. What type of statistical method does this illustrate—descriptive or inferential?

Why?