Practice 1 Solutions

1. A park ranger wants to estimate the deer population in Coventry Woods. She divides the forest into a grid, randomly selects a starting grid square, and then surveys every fifth grid square to count the number of deer.

B) Deer population in Coventry Woods

2. The Marshalton School District wants to understand how parents feel about online learning. They divide parents into groups based on the grade level of their oldest child (elementary, middle, high school). Then, they randomly select a proportional number of parents from each group to participate in a survey.

C) All parents in the Marshalton School District

3. A statewide grocery store chain wants to assess customer satisfaction in the geographic regions in which the stores are located. The chain randomly selects 3 of the 10 geographic regions and surveys customers entering those regional stores on a specific day.

D) Customers of a grocery store chain

4. The principal wants feedback from students on the new lunch menu. She puts all 1,200 student names into a hat and draws out 50 names without looking. These 50 students will be surveyed.

A) 1,200 students

5. A librarian wants to survey library patrons about their satisfaction with the new digital resources. Every hour, on the hour, for one day, the librarian approaches every fifth person who checks out a book and asks them to complete a short survey.

B) Library patrons

6. A wildlife biologist is studying the health of the crayfish population in a lake. They net a large number of crayfish and then randomly select 30 crayfish from the net to take blood samples and measure their length and weight.

A) Crayfish in the lake

7. Why is it important that being selected for a sample is randomized?

Sample: Random selection ensures that each person has an equally likely chance of being selected to represent the population, thereby minimizing bias.

8. What is the reason for having many sampling methods in statistics?

Sample: There are many sampling methods to ensure the sample matches the purpose of the study, is taken fairly, and is representative of the population.

9. Do you prefer the delicious taste and superior quality of Brand X coffee over other bland coffee brands?

Bias: “delicious taste,” “superior quality,” “bland”

Sample: What is your preferred brand of coffee?

10. Given the obvious advantages of playing video games for improving problem-solving skills, what is the minimum number of hours a day students should be allowed to play?

Bias: “obvious advantages,” “minimum number of hours”

Sample: How much time, if any, should students play video games each day?

11. A company wanted to know if its employees’ eyes were less strained if a screen filter was used during computer work. They selected 100 employees to participate. The list of participants was alphabetized, and the first 50 employees had a screen filter added to their computers without them knowing (treatment group). The remaining 50 employees did not have a screen filter (control).

Sample: Since the list of participants is alphabetized, it is not a random selection.

12. A call center tracked one employee’s first ten calls of the day. The employee was able to resolve seven out of ten calls in ten minutes or less each. On any given day, the call center receives an average of 375 calls. The call center reported: “Our representatives resolve 70% of all issues in under ten minutes per call.”

Sample: The sample is too small (only one employee and only the first ten calls of the day are tracked), and uses a percentage to make 70% sound better than seven out of ten.