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Exercises 6.5 Chapter Test

1.

To determine how community college students feel about current events, three history classes at City College are surveyed.

  1. Describe the target population of this study.

  2. Describe the sample of this study.

Answer.

  1. The target population is all community college students.

  2. The sample is the three history classes at City College that are surveyed.

2.

Classify each measurement as categorical or quantitative:

  1. Height of basketball players

  2. Astrological sign of movie stars

  3. Average annual snowfall in Denver

Answer.

  1. Quantitative

  2. Categorical

  3. Quantitative

3.

In each situation, indicate the type of sampling used:

  1. Every 25th shopper receives a survey.

  2. Readers are asked to give their opinion on a local tax by commenting on a tweet.

  3. The front row of a concert is asked to rate the performance.

  4. A researcher calls registered voters until they have talked to 50 men and 50 women.

  5. Student names are drawn out of hat to participate in a survey.

Answer.

  1. Systematic Sampling

  2. Convenience Sampling

  3. Convenience Sampling

  4. Quota Sampling

  5. Simple Random Sampling

Exercise Group.
In each situation identify a potential source of bias.
4.

The front row of a concert is asked to rate the performance.

Answer.

This survey may have sampling bias because those in the front row aren’t representative of everyone at the concert. It is possible that those in the front row had a different expericence (better sound, etc) than those sitting in other locations.

5.

An oil company releases a study that stating that all changes to global temperatures are due to natural variability.

Answer.

This is a self-interest study and may have bias because oil companies are impacted the fact that the use of fossil fuels are resulting in climate change.

6.

Readers are asked to give their opinion on a local tax by commenting on a tweet.

Answer.

This survey may have non-response bias. Typically, only those who feel very strongly about an issue will make comments about it. Those with opinions in the middle are less likely to respond. We are also only asking Twitter users, who are predominately male and most likely to be age 25 - 34.

7.

Customers are asked, “Did you enjoy our excellent delivery service?”

Answer.

This is a loaded question—the question implies that the service is excellent and doesn’t allow for the respondent to decide the quality of the delivery service.

8.

Is the scenario describing an observational study or an experiment?

A study took a sample of adult and asked them about their morning habits. The data showed that people who drink coffee were more likely to go to bed later than those who didn’t drink coffee.

Answer.

This is an observational study.

9.

How could we create observational study to test whether those who drink coffee go to bed later than those who don’t?

Answer.

We could select a group of people and assign half of them to drink coffee and the other half to not drink any coffee. We would ask the participants to record their bedtimes and compare the results.

10.

You want to determine if a vegetarian diet has an effect on blood pressure. You recruit 100 volunteers and randomly assign each a non-vegetarian diet plan or a vegetarian diet plan. At the end of two months, you record the original and final blood pressures for volunteer.

  1. Is this an observational study or experiment?

  2. Describe the control group and the treatment group.

Answer.

  1. Experiment

  2. The control group is those who were assigned the non-vegetarian diet and the treatment group is those who were assigned the vegetarian diet.

11.

To determine whether a new exercise program will reduce blood pressure, a researchers selects 100 students to participate in an experiment. Students who live on campus are asked to participate in the exercise program; those who don’t live on campus do not participate in the exercise program.

  1. Describe the control group and the treatment group.

  2. Is this a blind or double-blind study?

  3. Why might the results of this study be unreliable?

Answer.

  1. The control group is the students who don’t live on campus and aren’t not participating in the exercise program. The treatment group is those who live on campus and participate in the exercise program.

  2. No. Participants, as well as researchers, will know if they're are doing the exercise program.

  3. Confounding variables may impact the results. Other factors, like age, gender, weight, etc impact blood pressure. It is possible that those who live on campus have different demographics than those who don’t live on campus.