Type of Bias:
Sampling
Measurement
Both
None

Dr. Cloud is conducting interviews with students at Davisville and Springville High School to determine the rate of smoking among American teenagers. Dr. Cloud gets a list of all the students from both high schools and randomly selects 50 students from each school. An appointment for the interview is scheduled with the students and their parents. Students are interviewed with their parents in the room. The students are asked questions such as "Do you smoke regularly?" "Have you ever smoked?" and "What percentage of your friends smoke?" After finishing the interviews, Dr. Cloud concluded that only 1% of American teenagers smoke regularly and 18% of teenagers have tried smoking.

Dr. Garcia is using both observations and interviews to investigate the rate of smoking among American teenagers. She first selected three study sites: one urban, one rural, and one suburban. Dr. Garcia went to one high school in each study site and interviewed 25 students from each school. The principal of each school selected the 25 students who would be interviewed for Dr. Garcia's study. Of the 75 total students, only three said that they smoked regularly (4%). Taking the average percentage from her observations and interviews, Dr. Garcia concluded that approximately 16% of American teenagers smoke.

Dr. Nandi is using confidential interviews to estimate the rate of smoking among American teenagers. She contacted principals at three high schools (rural, urban, and suburban) and asked for a list of their student body. After randomly selecting 50 students from each school, Dr. Nandi gave each student a permission slip and confidentiality form to be signed by their parents stating that their child was participating in the study and they, as parents, would not have access to the file on their own child. Roughly 35 students from each school returned the permission slip and confidentiality form. Students were asked fifteen questions about their experiences with smoking. Dr. Nandi found that out of the three high schools, 53% of students had tried smoking and 25% smoke a half pack of cigarettes or more a day.

Dr. Wellstone is using a shadowing method to study rates of smoking among American high school students. First, Dr. Wellstone hired 50 college freshmen and sophomores. During the hiring process, Dr. Wellstone made certain that the hired students blended in well with the high school students being sampled. He then received a list of students attending Davisville and Springville High Schools and randomly selected 25 students from each school. Each college student Dr. Wellstone hired shadowed one of the selected high school students from 3 pm to 5 pm as well as at any parties the high school students attended. After shadowing the high school students for two consecutive weeks, the hired college students recorded whether or not their study subject smoked and, if so, how often. Dr. Wellstone concluded that 28% of American teenagers smoke regularly and 44% will smoke at weekend parties only.

Incorrect. Please try again.
Correct! Having the parents in the room observing while the survey is conducted creates measurement bias. Few students will admit in front of their parents that they smoke so there will likely be an underestimation of the teenage smoking rate.
Correct! Although selecting students from one urban, one rural, and one suburb was a good sampling technique, using students selected by the principal may give an underestimation of the teenage smoking rate.
Correct! Requiring the permission slips to be returned creates sampling bias. If only the students who returned the permission slip were able to participate, the sample group is not representative of the entire student population.
Correct! Observing students for only 2 hours of the day may result in an underestimation of the rate of teenage smoking. Students who smoke in the morning or at night (not at parties) may not be counted as smokers. By the same logic, the percentage of teenagers that smoke only at parties may be an overestimation since some of those smokers may smoke at other times, but not during the 3 pm to 5 pm observation hours.