Sample and Inference

A fitness center asked 80 random patrons how long they

exercise on average each day. Results are shown in the table to

the left. If 300 people come to the gym on a given day, approximately how many would you expect to exercise for more than 135 minutes?

• 15 people

• 72 people

• 120 people

• 214 people

Andre wants to survey a random sample of the student body in his school to find out which day after school would work best for students to do volunteer work for a local charity. Which sample would best represent the student body?

• asking twenty students waiting in line for lunch

• asking one person from the seventh grade daily for twenty days

• asking twenty students on their way to the bus after school

• asking one person each from twenty different classrooms during the first class period

Lucy collects data from a random sample of seventh-graders. Out of 40 respondents, 7 attend after-school programs. Of the 200 seventh-graders attending Lucy’s school, how many would be expected to attend afterschool programs?

Caleb is comparing the growth of plants using two different fertilizers. Use the measures of center from the box plots to make an inference about the data.

• Based on the means, plants in Group A grew more than plants in Group B

• Based on the means, plants in Group B grew more than plants in Group A.

• Based on the medians, plants in Group A grew more than plants in Group B

• Based on the medians, plants in Group B grew more than plants in Group A.

The dot plot shows a random sample of the number of fish caught and released by 30 participants during a two-day fishing derby.

Use the mean value of each data set to make an inference about the number of fish caught each day.

• On average, most participants caught and released 5 or more fish.

• More participants caught 6 fish than any other number.

• The same participants who caught and released 1 fish the first day caught and released 1 fish the second day.

• On average, participants caught and released more fish on Day 2.

Margo wants to convince her father to change her curfew from 9 P.M. to 10 P.M. She gathers data on curfew times from a random sample of students at her middle school. Can Margo use these data to present a valid inference that will convince her father? Explain.

• Yes; Most students have a curfew of 10 P.M. or later.

• Yes; More students have a curfew of 9 P.M. than any other time.

• No; Most students have a curfew of 9 P.M. or earlier.

• No; More students have a curfew of 10 P.M. or 11 P.M. than 8 P.M.

Russell randomly surveys seventh-graders in his school and finds that 6 of 30 attend summer camp. If there are 200 seventh-graders in his school, about how many are expected to attend summer camp? Enter your answer in the box.

Group A and Group B were randomly sampled from the same population. Select all the inferences that you can make.

• Group B has a higher median than Group A.

• Group B has a higher mean than Group A.

• Group B has more overall variability than Group A.

• Group B has a smaller range than Group A.

• Group A and B have the same maximum value.

If you compare the medians of each data set, who spends more time online?

• Seventh graders

• Eighth graders

• Both grades spend an equal amount of time online.

• Impossible to determine from the data sets.

The Magic Kingdom theme park has many attractions, one of which is Space Mountain. Are the people who ride Space Mountain the population, or a sample, of the theme park? Explain.

• Population. They are all the people at the theme park.

• Sample. They are a subset of all the people at the theme park.

• Both population and sample. They are all the people at the theme park

• Neither population nor sample. They are not the people at the theme park.