An AP Statistics class starts a project to estimate the average number of hours a student at their high school sleeps per night. Their high school has 1200 students, and they take a sample of the first 120 students that arrive at school on a particular day. They ask each of the 120 students how many hours of sleep they got the night before and then calculate an average.

Which of the following statements is an accurate description of the elements of this survey?

(A) Population: the 120 students surveyed. Parameter of interest: the average number of hours a student at this high school sleeps per night.
(B) Sample: the 1200 students of the school. Population: all high school students in the United States. Statistic: the average number of hours a student at this high school sleeps per night
(C) Sample: the 120 students surveyed. Population: the 1200 students at the high school. Parameter of interest: the average number of hours a student at this high school sleeps per night.
(D) Sample: the 120 students surveyed. Population: the 1200 students at the high school. Statistic: The average number of hours a student at this high school sleeps per night.
(E) This is not a survey because a convenience sample was used.

To estimate the average number of hours a student their highschool sleeps per night, the students of the statistics class took as sample the first 120 students that arrived at the school on a particular day, out of the 1200 student population, and asked how many hours of sleep they got the night before.

The population of interest is the entire group of experimental units that exists in the world, in this example is the student body of the high school: 1200 students.

The sample is formed by the students that were interviewed: 120 students.

The parameter of interest is the average sleep time per night of the students in high school.

Correct answer:

(D) Sample: the 120 students surveyed. Population: the 1200 students at the high school. Statistic: The average number of hours a student at this high school sleeps per night.