Samples Surveys and Inferences

There are 400 students at Polly's school. She surveyed a random sample of 80 students to find their favorite hobby. 19 said they like to read. 30 said they like to be with friends. 8 said they like to do crafts. 23 said they like to play sports. Polly infers that doing crafts is the least popular hobby at her school. Yovani estimates that about 200 students in the school favor playing sports as a hobby. Do you agree?

• Yes, I used a proportion to find the number of students in the school who likely to prefer to play sports. 23/80 = 200/400; 200 students

• No, I used a proportion to find the number of students in the school who likely to prefer to play sports. 23/80 = 115/400; 115 students

The two data sets show the number of days that team members trained before a 5k race. What inference can you draw by comparing the median?

• There is more variability in the number of days that Team A members trained because the IQR for Team A is greater than the IQR for Team B.

• There is more variability in the number of days that Team B members trained because the IQR for Team B is greater than the IQR for Team A.

• Team A members generally trained for more days than Team B members

• Team B members generally trained for more days than Team A members

What inference can you draw by comparing the interquartile ranges?

• There is more variability in the number of days that Team A members trained because the IQR for Team A is greater than the IQR for Team B.

• There is more variability in the number of days that Team B members trained because the IQR for Team B is greater than the IQR for Team A.

• Team A members generally trained for more days than Team B members

• Team B members generally trained for more days than Team A members

A school principal wants to see which subject the 695 students in his school liked best. Which choice BEST represents a representative sample?

• The girls in the school.

• 1 classroom for each grade

• All the students in the school.

• The students making a B in math.

A factory manufactures light bulbs. The factory currently has 300 boxes of light bulbs in its warehouse. To test the quality of bulbs, Alex decides to take out a sample of bulbs and test them to see if they work. Which surveying method will give him the LEAST valid results?

• selecting ten boxes randomly, mixing the bulbs of these boxes together and then selecting ten bulbs randomly

• selecting ten boxes randomly and then selecting one bulb randomly from each box

• selecting one bulb randomly from every tenth box

• selecting one box randomly and then selecting all the bulbs from the box

Students in Ms. Willis’s math class wanted to know the favorite snacks of students in the school. How could they generate a random sample to survey?

• Line up the students by height and choose the first 20 students

• Use the school roster and randomly choose 50 boys.

• Obtain an alphabetized list of all the students in the school and select every seventh student

• Place all the names of the students in Ms. Willis's math class in a hat and randomly select 10 students.

As part of a 7th grade statistics project, the teacher brings a candy jar full of gumballs (red & green). The assignment is to estimate the proportion of red gumballs in the jar. Suppose one of the students draws 25 gumballs from the jar: 8 are red, 17 are green. What is the SAMPLE?

• 25 gumballs drawn

• all gumballs in the jar

• the students

• the 17 green gumballs

Mrs. Seats is conducting a survey to find out the favorite snack of sixth and seventh graders. She will ask a sample of 100 students. Which of the groups below should be surveyed to get the BEST representative sample?

• 100 students at the movie theater

• the first 100 students who go to a local baseball game

• 5 students from each of the 20 local middle schools

• 20 random students from each of the 5 local sixth- and seventh-grade schools

The counselors at a camp are scheduling activities for family visitation day. They decide to conduct a survey to determine which activities campers would most like to share with their families. Which describes a method for getting a sample that is both representative and random?

• During the dinner hour, announce that any camper interested in doing so can collect and complete a survey.

• During camp free time, ask every fifth camper in the arts and crafts hall to complete a survey.

• During morning roll call, ask every tenth camper to complete a survey.

• During camp free time, ask all campers down at the lake to complete a survey.

• 14 7th graders

• 28 7th graders

• 35 7th graders

• 42 7th graders