Practice 2 Solutions

1. A quality control manager at a light bulb factory wants to check the lifespan of a batch of 10,000 light bulbs. He uses a random number generator that selects 100 light bulbs from the production line for testing.

A) The batch of 10,000 light bulbs

2. A city planner is studying traffic patterns on Champion Avenue. They set up a camera that records cars passing a specific point. Starting at a random minute in the hour, they record the average traffic speed every ten minutes for a full day.

B) All cars on Champion Ave

3. A factory manager needs to inspect a batch of 500 newly manufactured car parts for defects. They line up all the parts, pick a random starting part, and then inspect every 20th part on the line after that.

B) The batch of 500 newly manufactured car parts

4. A national research organization wants to survey adults in a specific state about their exercise habits. They divide the state into counties (geographic regions), randomly select 15 counties, and then survey every adult residing in those selected counties.

D) Adults in a specific state

5. A university wants to understand student opinions on a new campus policy. They divide the student body into undergraduate, graduate, and doctoral students. From each of these groups, a proportional number of students is randomly selected to participate in a survey.

C) Students attending the university

6. A company is conducting a prize drawing for its employees. They assign a unique number to each of the 250 employees and then use a random number generator to pick ten winning numbers.

A) Company employees

7. Because everyone wants to be stylish, what brand name clothing is the best?

Bias: Assumes everyone cares about being stylish, and that stylish brands are the best.

Sample: What is your favorite brand of clothing?

8. As a person who cares about the environment, don’t you agree that nothing else should ever be printed on paper in order to save the trees?

Bias: Telling the person that they care about the environment, “don’t you agree?”

Sample: What are some suggestions for reducing the impact of paper use on the tree population?

9. An advertisement for a new job-search website claims that people who use the site are highly successful. The ad states that users have a 200% higher chance of finding a job. A footnote clarifies that this is based on a comparison to a baseline control group of non-users who had a 1% chance of finding a job.
The claim: “Use our site for a 200% higher chance of finding your dream job!”

Sample: 3% is mathematically 200% larger than 1%. The numbers are so small that the website is unlikely to be the primary cause of finding a job. The 200% is used to make the numbers seem better than they are.

10. A university randomly selected 500 college seniors to ask them how many hours per week they spent studying and what their final GPA was for that semester.
    The report: The researchers concluded that there is a strong positive relationship between the two variables.

Sample: The observation does not have enough evidence to prove that studying more hours results in a higher GPA.