Name: ______Date: ______Hour: _____
1. Members of a research team are considering three studies related to sleep and learning. The first study involves comparing the scores on a post-study test of learning from two groups of randomly chosen adults, with one group getting at least 7 hours of sleep per night for a week and the other group getting at most 6 hours of sleep per night for a week. A second study involves asking a random sample of students at a large university to report the average number of hours of sleep they get each night and their college grade point average. A third study involves asking a random sample of high school students in a large school district whether they feel they get enough sleep to stay alert throughout the school day.
a. Which study appears to look for an association between two variables without actively manipulating either one? What are those variables?
b. Which study appears to be looking for evidence that one variable actually influences another variable? What are those variables, and which one is manipulated to see if it influences the other?
c. Which study appears to be simply measuring a variable in a population? What is that variable?
Explain why the results of each survey are likely to be inaccurate and then suggest a way to improve the accuracy of the survey.
2. A store offers its customers a chance to win a cash prize if they call a toll-free number on a receipt and participate in a customer satisfaction survey.
3. A reporter for a local newspaper asks a random sample of people attending a holiday parade, “Since this holiday parade is so popular, do you support having the city provide the support for a larger parade next year?”
Determine whether each research study is an observational study or an experiment. Identify the factor if it is an observational study or the treatment if is an experiment. Also identify the characteristic of interest.
4. Researchers found that of patients who had been taking a bone-loss drug for more than five years, a high percentage of patients also had an uncommon type of fracture in the thigh bone.
5. Researchers found that when patients with chronic illnesses were randomly divided into two groups, the group that got regular coaching by phone from health professionals to help them manage their illnesses had lower monthly medical costs than the group that did not get the coaching.
6. A caretaker at a zoo is studying the effect of a new diet on the health of the zoo’s elephants. She continues to feed half of the elephants their existing food, switches the other half to a new diet, and then monitors the health of the elephants.
7. A school district wants to know whether there is a relationship between students’standardized test scores and the amount of time they spend on extracurricular activities. The school board surveys students from each school in the system to gather data about the average number of hours per week spent on extracurricular activities and each student’s most recent test scores.
8. Researchers want to know the effect of vitamin C as a dietary supplement on blood pressure. Half of the randomly assigned subjects take one 1000-milligram tablet of vitamin C daily for six months while the other half of the subjects take one placebotablet daily for six months. The blood pressure of all subjects is taken weekly.
Identify the treatment, characteristic of interest, control group, and treatment group for the given experiment. Assume all subjects of the research are selected randomly.
9. A restaurant manager wants to know whether to keep using orange slices as a garnish or to change to tangerine slices. All of the subjects are blindfolded. Half of the subjects are asked to eat orange slices, and the other half are asked to eat tangerine slices. All subjects are asked whether they like the taste of the fruit.
10. A pharmaceutical company wants to know about the side effects of a new cholesterol medication. Out of 400 randomly selected volunteers who currently take the existing cholesterol medication, the researchers switch the old drug with the new drug for 200 of them, and continue to give the other 200 the old drug. They then monitor the two groups for side effects.
11. A park service wants to determine whether reintroducing a particular species of underwater plant to the lakes in the park system would be beneficial to a particular species of fish living in the lakes. The researchers reintroduce the plant in one lake. One year later, they study the health of the fish population in the lake where the plant was reintroduced, as well as in an ecologically similar lake without the plant.
12. A research team wants to know whether a new formula for a laundry detergent is more effective than the existing formula. The team members first wash a variety of fabrics with a variety of stains using the detergent with the new formula, and then they wash the same pairings of fabrics and stains using the detergent with the existing formula. They then compare the extent to which the stains have been eliminated.