Conducting a Study and Statistics Planning Practice Questions (page 2)
To review these concepts, go to Conducting a Study and Statistics Planning Study Guide.
Conducting a Study and Statistics Planning Practice Questions
The Chamber of Commerce of a certain city was planning a campaign to encourage the city's residents to shop within the city. Before beginning the campaign, the Chamber decided to determine how often people were shopping outside of the city. They conducted a telephone survey. Telephone numbers of households in the city were randomly selected (how this might be done will be discussed in Lesson 14). The selected numbers were called until 400 responses were obtained. An adult at each household in which the phone was answered was asked, "How many times in the past week have you shopped outside of this city?" Give an example of each of the following potential sources of bias and describe how it might affect the estimate of the average number of times that a person in this city has shopped elsewhere during the past week.
a. selection bias
b. response bias
c. nonresponse bias
- An ornithologist (one who studies birds) wants to determine the kinds and numbers of birds that inhabit an area along an abandoned railroad track that is to become a walking path. Each morning, she goes to a randomly selected point along the track and walks 50 yards north, identifying the kinds of birds and the numbers of each kind within 10 yards of the track. She is able to clearly see all birds on, or right by, the track, but because of the tall grass and shrubs, it becomes more difficult to see birds the farther they are from the track. She then determines the average numbers of each kind within a ten square-yard area. What type of bias might she encounter and how might it affect the estimates?
For each of the following studies, specify the following:
a. the response variable of interest
b. the population to which inference may be made
c. the types of conclusions (cause and effect or associations) that can be drawn
d. the type of study
- A drug company advertises for people to participate in a study on cholesterol. Those who answer the ad and pass the initial screening are randomly assigned to use either a standard medication or one that has recently been developed. After one month, the cholesterol level of each participant is measured.
- A cable television company sends a questionnaire to 100 randomly selected customers to determine whether they would be willing to pay more if a new set of channels was added to the standard package.
- A kindergarten teacher wants to study whether or not children who have been in day care learn the alphabet more rapidly than those who stay at home. After teaching the alphabet for the first month of school, the teacher randomly shows the letters to each student and records the number of correct responses. He also determines which children were in day care for at least one year prior to the start of school.
- A large dental school wants to compare two approaches to cleaning teeth to determine which one takes less time. Among the patients who have teeth cleanings scheduled during the next six months, 60 are randomly selected and asked to participate in the study. Half are randomly assigned to have their teeth cleaned using one of the methods; the other half have their teeth cleaned using the other method. The time required to clean each person's teeth is recorded.
a. Only people with telephones could participate in the survey. People without telephones may be less likely to shop outside the city, causing the mean number of times people who shop outside the city to be underestimated.
b. People might want to show support for their city, causing how often they shop outside of the city to be underestimated.
c. People with lower incomes who can't afford to shop very often might be more reluctant to participate, causing the mean number of people who shop outside the city to be underestimated.
- Measurement or response bias: She tends to undercount the birds farther from the track causing her to underestimate the average number of each kind within a ten-square yard area.
a. The cholesterol level of a participant after one month
b. The people who participated in the study, narrow scope of inference
c. Cause-and-effect conclusions can be made to determine the effect of the standard medication versus the effect of the recently developed medication
d. Experiment, narrow scope of inference
a. Whether or not the customers would be willing to pay more
b. All customers of the cable television company, broad scope of inference
c. Associations can be concluded for the population as to whether or not people would be willing to pay more if a new set of channels was added.
d. Sample survey
a. The number of correct responses from the students when shown the letters
b. The students in the class, narrow scope of inference
c. Cause-and-effect conclusions cannot be made.
d. Observational study
a. The time required to clean the teeth
b. All patients who have their teeth cleaned at this large dental school during this six-month period, broad scope of inference
c. Cause-and-effect conclusions can be made.
d. Experiment, broad scope of inference
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