Title: Types of Statistical Studies and Producing Data
Course: Question Banks

Q: Which research question is poorly stated because it does not specify a population?
- What is the average commute time for faculty working at a community college in California? (This research question is well-stated. The population is faculty working at a community college in CA. The information we are gathering is commute time. We want to estimate the average commute time for this population.)
- What proportion of college students take online classes? (This research question is well-stated. The population is college students. The information we are gathering is whether or not the student is taking an online class. We want to estimate the proportion of college students taking online classes.)
- What is your commute time when you drive to school? (This question is poorly stated. Here is an improved version: What is the average commute time for students attending Contra Costa College?)
A: What is your commute time when you drive to school?

Q: Which of the following questions is stated as a cause-and-effect question?
- Is lack of health insurance linked to shorter life expectancy? (This question suggests a relationship may exist between health insurance and how long we live, but the word “linked” does not suggest that the relationship is a cause-and-effect relationship.)
- Does tutoring correlate with improved performance on exams? (This question suggests a relationship may exist between tutoring and higher exam grades, but the word “correlate” does not suggest that the relationship is a cause-and-effect relationship.)
- Is maternal smoking associated with low birth weight? (This question suggests a relationship may exist between smoking and low birth weight, but the word “associated” does not suggest that the relationship is a cause-and-effect relationship.)
- Do instructors who learn their students’ names receive higher ratings on student evaluations? (This question suggests that learning students’ names leads to higher ratings for instructors. This is an implied cause-and-effect relationship.)
A: Do instructors who learn their students’ names receive higher ratings on student evaluations?

Q: Reuters reported the results of a July 8, 2016 poll about the 2016 U.S. presidential election. Among the 3,510 respondents, 31.7% of those polled selected “Donald Trump (Republican)”.

This is an observational study designed to answer a question about a population. Who is the population?
- The 3,510 U.S. adults polled (The 979 people are the sample.)
- U.S. adults who read materials from Reuters (Reuters reported the results of this poll. But the goal of this poll is to make a statement about a population.)
- The 31.7% who answered “Donald Trump (Republican)”. (This is the result of the poll, but the goal of this poll is to make a statement about a population.)
- All U.S. voters (The goal of this poll is to make a statement about all U.S. voters to estimate the results of the presidential election.)
A: All U.S. voters

Q: Which question is best answered by an experiment?
- Is there an association between the number of hours college students spend each week on volunteerism and their college GPA? (This question is about an association between two variables. It is best answered by an observational study. It would be very difficult to design an experiment to show a cause-and-effect relationship between volunteer hours and GPA.)
- Do the majority of community college students plan to transfer to a four-year institution? (This question is about estimating the proportion of a population that will transfer to a four-year institution. It can only be answered by an observational study.)
- Does a mandated student loan orientation reduce student loan default rates for community college students? (This question is about establishing a cause-and-effect relationship between a mandated student loan orientation and student loan default rates for community college students. An experiment is the best way to establish a cause-and-effect relationship.)
A: Does a mandated student loan orientation reduce student loan default rates for community college students?

Q: In a study of cell phones and the risk of brain cancer, researchers studied a group of 469 people with brain cancer. They paired each person who had brain cancer with a person of the same sex, of similar age, and the same race who did not have brain cancer. Then they compared the cell phone use for each pair of people. The Journal of the American Medical Association published the results in 2000 in an article titled “Handheld Cellular Telephone Use and the Risk of Brain Cancer.”

Pick the best description of this study:
- an observational study to make an estimate or a claim about a population (You are right that this is an observational study. But there are two variables in the study.)
- an experiment to establish a cause-and-effect relationship between two variables (You are right that there are two variables: “cell phone use” and “brain cancer.” But the researchers did not manipulate the amount of cell phone use to study the effect on brain cancer. So this is not an experiment.)
- an observational study of an association between two variables (This is an observational study of the association between cell phones and brain cancer.)
A: an observational study of an association between two variables

Q: In June 2011 The Washington Post published the results of a poll about the war in Afghanistan. In the poll 1,502 U.S. adults answered the question, “Do you think the U.S. made the right decision or the wrong decision in using military force in Afghanistan?”

Pick the best description of this study:
- an observational study of an association between two variables (A poll is an observational study. But there is only one variable in this study: “opinion about the war in Afghanistan.”)
- an experiment to establish a cause-and-effect relationship between two variables (A poll is an observational study.)
- an observational study to make an estimate or a claim about a population (A poll is an observational study. With the data from this poll we can estimate the proportion of U.S. adults who think the U.S. made the right decision in using military force in Afghanistan.)
A: an observational study to make an estimate or a claim about a population

Q: Football: Research presented at the 2016 American Academy of Neurology meeting shows retired NFL players tested in the study have a much higher rate of traumatic brain injury than the general public. The study administered sensitive brain scans called DTI instead of traditional MRI scans as well as thinking and memory tests.

Which question is this observational study designed to answer?
- Is the DTI scan better than the MRI scan at detecting brain trauma? (This study does not collect information on MRI scans.)
- What is the rate of brain trauma of football players? (This study sample focuses on retired NFL players who are not representative of all football players.)
- What is the rate of brain trauma of retired NFL players? (This observational study collects information on brain injuries from a sample of retired NFL players that can be used to make an estimate about the population of NFL players.)
A: What is the rate of brain trauma of retired NFL players?

Q: Obesity and Diabetes Risk: In a Gallup-Healthways Well-Being Index poll, a random sample of 484,350 adults residing in the U.S. and the District of Columbia were asked to self-report their weight and height and answer the question “ Has a doctor or nurse ever told you that you have diabetes?”.

According the Gallup’s analysis, “Obese adults between the ages of 25 and 64 are at least four times more likely to have been diagnosed with diabetes than those who are normal weight, according to the Gallup-Healthways Well-Being Index. “

Which question is this observational study designed to answer?
- What proportion of the U.S. population has been diagnosed diabetic from a physician? (This is only one of the questions asked in the study along with the weight and height of the patient. What question might these three pieces of information help one answer?)
- For each sex, age, and weight, does higher calorie intake cause higher rates of diabetes? (The researchers did not manipulate people's calorie intake to study the effect on diabetes diagnoses. This is an observational study which can only support association, not causation.)
- Is obesity (based on weight and height) associated with a diabetes diagnosis? (This observational study collects information on height and weight from a sample of humans with and without diabetes to make an estimate about the difference in diabetes rates between those determined obese vs those determined to be of normal weight for their height.)
A: Is obesity (based on weight and height) associated with a diabetes diagnosis?

Q: Opinion Poll: In March 2017, Gallup published the results of a poll about environmental concerns. In the poll 1,018 U.S. adults responded “worry about this problem a great deal, a fair amount, only a little or not at all.” to a list of environmental problems. To the prompt “pollution of drinking water”, 63% responded they worry a great deal and 57% worry a great deal about pollution of rivers, lakes and reservoirs

Which question is this observational study designed to answer?
- What proportion of Gallup poll responders feel worried about the water pollution? (The Gallup poll responders represent the sample. What population is this poll trying to estimate?)
- What proportion of U.S. adults feel worried about the environment? (This observational study does not measure this broader question of general concern for the environment.)
- What proportion of U.S. adults feel worried about water pollution? (The goal of this observational study is to estimate U.S. adult sentiment regarding water pollution..)
A: What proportion of U.S. adults feel worried about water pollution?

Q: An article titled "Guard Your Kids Against Allergies, Get Them a Pet" (San Luis Obispo Tribune, August 28, 2002) described a study that led researchers to conclude that "babies raised with two or more animals were about half as likely to have allergies by the time they turned six."

Which of the following is a potential factor that could confound the relationship cited?
- Two or more animals in the home (The study describes an association between the number of animals in the home and whether or not the child has allergies. The explanatory variable is the number of animals in the home; therefore, this is not a confounding factor. Confounding factors are not measured or monitored in a study. Additionally, there is at least one correct answer.)
- Early exposure to animals (The study describes an association between the number of animals in the home and whether or not the child has allergies. So researchers are intentionally monitoring early exposure to animals; therefore, this is not a confounding factor. Confounding factors are not measured or monitored in a study but could be responsible for the observed association. Additionally, there is at least one correct answer.)
- Whether or not the child has allergies (The study describes an association between animals in the home and whether or not the child has allergies. The response variable is whether or not the child has allergies; therefore, this is not a confounding factor. Confounding factors are not measured or monitored in a study. Additionally, there is at least one correct answer.)
- Whether or not the parents have allergies (The study describes an association between the number of animals in the home and whether or not the child has allergies. This association could be explained by whether or not the parents have allergies; therefore, this is a potential confounding factor. Parents without allergies are more likely to have pets. In addition, parents without allergies are more likely to have children without allergies.)
A: Whether or not the parents have allergies

Q: Suppose that your college administration wants to charge a $100 fee per term for a reserved parking space on campus. The administration wants to know the percentage of students at the college who would support this fee. Which sampling plan will best represent the opinions of students at your college?
- Choose four 8 a.m. classes at random. Survey all of the students in each of these classes. (Students taking 8 a.m. classes probably do not have much trouble finding a parking space. So their responses may not represent the concerns of students who attend classes during the busier day time hours.)
- Stand in one of the most crowded parking lots and interview students as they get out of their cars. (This is a convenience sample. It will overrepresent the opinions of those frustrated with the parking situation.)
- Hand out a survey to all students who have a parking ticket. (This is a convenience sample. It will overrepresent the opinions of those frustrated with the parking situation.)
- When students register online, the question appears in a pop-up window that must be answered in order to proceed with registering. If students register in person, make them answer the question before their registration is processed. (Since all students have to register, everyone has the opportunity to participate. Here we are not sampling at all!)
A: When students register online, the question appears in a pop-up window that must be answered in order to proceed with registering. If students register in person, make them answer the question before their registration is processed.

Q: Here is an excerpt from a study published by the Pew Research Center in 2011 titled "Teens and Digital Citizenship Survey.”

"In 2011 Teens and Digital Citizenship Survey ... obtained telephone interviews with a nationally representative sample of 799 teens ages 12 to 17 years old and their parents living in the continental United States. A combination of landline and cellular random digit dial samples was used to represent all teens and their parents in the continental United States who have access to either a landline or cellular phone."

The survey describes a "nationally representative sample." Which feature of the sampling plan is necessary in order for the sample to be representative of the population?
- A large sample, such as the 799 teens and their parents (A large sample is not necessary for the sample to be representative of the population. In fact, large samples can be biased and not represent the views of the population. We saw this in the example where 2 million people were polled during the 1936 presidential election, but the sample did not represent the views of the population.)
- A reputable organization conducting the study (such as the Pew Research Center) (Organizations that specialize in polling, such as the Pew Research Center or Gallup, use appropriate sampling methods, but a sample can be representative of a population even if it is not gathered by a professional organization. In addition, a reputable organization is not a guarantee that the sampling method is appropriate. We saw in the example of the 1936 presidential election, the reputable magazine Literary Digest used an inappropriate sampling method.)
- A random sample, such as the random digit dials used to choose the phone numbers (A random sample reassures us that the sample is representative of the population.)
A: A random sample, such as the random digit dials used to choose the phone numbers

Q: Suppose that you want to estimate the proportion of students at your college that read the college newspaper. Which sampling method is the best for producing this estimate?
- Select 50 students at random from the college. (This is a good method because it uses random selection. But there is a better option.)
- Select 200 students at random from the list of students enrolled in Journalism courses. (This option will probably produce biased results. Students taking a Journalism class are more likely to read the college newspaper.)
- Select 300 students who pick up the school newspaper from the library. (This option will produce biased results because every student in the sample is reading the college newspaper!)
- Select 100 students at random from the college. (Like option (a), this is a good method because it uses random selection. But it is better than (a) because larger samples tend to be more accurate.)
A: Select 100 students at random from the college.

Q: Which of the following is an example of a census?
- Poll students at a college by including a pop-up window in the online registration form. Students have to answer the survey questions before they can register. Try to catch the remaining students at the admissions window when they register in person. (All students have to register for classes. If all the students registered online, this would be a census because they have to answer the questions before registering. So everyone would answer. But not all students register online.)
- Survey parents whose children attend a local elementary school by randomly selecting 50 parents from the school’s records. (This is a random sample, not a census.)
- The U.S. Population Census (The U.S. Population Census does not actually gather information from everyone living in the U.S. A full census is only possible for small populations.)
- Weigh every child at an elementary school for a study of physical fitness at the school. (If you weigh EVERY child at the elementary school, this is a census.)
A: Weigh every child at an elementary school for a study of physical fitness at the school.

Q: Researchers at the University of Wisconsin at Madison conducted an experiment to study the effect of meditation on the immune system. The researchers randomly assigned volunteers to one of two treatments. One group completed an 8-week course in meditation and actively practiced meditation during this period. The other group received no meditation training and did not meditate during the 8-week period.

At the end of the experiment researchers gave the subjects a flu shot. A healthy immune system will produce antibodies in response to a vaccine. At 4-weeks and 8-weeks after the flu shot, researchers did a blood test to measure the levels of antibodies produced against the vaccine. Both groups had an increased level of antibodies, but the meditators had a significantly greater increase in antibodies than the non-meditators. Psychosomatic Medicine published the results in 2003 in an article titled “Alterations in Brain and Immune Function Produced by Mindfulness Meditation.”

Which of the following is NOT part of the experiment design?
- random assignment (Random assignment is part of this design. Volunteers were randomly assigned to one of the two treatments.)
- use of a control group (Use of a control group is part of this experiment. The control group is the group who did not meditate.)
- double-blinding (It is not possible for this experiment to be double-blind. The participants will know which treatment group they are in because they have to meditate or abstain from meditation. Also, it is not important to blind the researcher in this situation since there is no subjectivity in measuring the level of antibodies in blood.)
A: double-blinding

Q: Researchers at the University of Wisconsin at Madison conducted an experiment to study the effect of meditation on the immune system. The researchers randomly assigned volunteers to one of two treatments. One group completed an 8-week course in meditation and actively practiced meditation during this period. The other group received no meditation training and did not meditate during the 8-week period.

At the end of the experiment researchers gave the subjects a flu shot. A healthy immune system will produce antibodies in response to a vaccine. At 4-weeks and 8-weeks after the flu shot, researchers did a blood test to measure the levels of antibodies produced against the vaccine. Both groups had an increased level of antibodies, but the meditators had a significantly greater increase in antibodies than the non-meditators. Psychosomatic Medicine published the results in 2003 in an article titled “Alterations in Brain and Immune Function Produced by Mindfulness Meditation.”

Stress can harm the immune system. So stress could be a confounding factor in this experiment. Which of the following features of the experiment design is the best way to control the effects of stress on the results of the experiment?
- use volunteers (people who have time to volunteer for a study are probably not stressed out by a busy life) (This statement may be true, but it may also be false. Volunteers for this experiment may also be ill and experiencing stress from illness. Use of volunteers is not a good way to make sure that the stress level will be similar in the two groups.)
- use a control group for comparison (Use of a control group provides a baseline for comparison. But the way we assign subjects to treatment groups is what is important for controlling the effect of stress on the results. We control the effect of stress on the results by making groups with similar stress levels.)
- use random assignment to treatment groups (Random assignment creates groups with similar levels of stress. So stress will affect both groups similarly. Thus any differences in immune systems is not due to differences in stress, but rather to meditation.)
A: use random assignment to treatment groups

Q: Imagine that you are a researcher working on a cure for Alzheimer’s disease. You develop a drug that you think could help people suffering from Alzheimer’s. To assess the effectiveness of the drug, you conduct a randomized comparative experiment. You find that 40% of patients taking a placebo report improvements, but 80% of the patients taking your new drug show improvement.

What can you conclude from these results?
- The placebo effect is not present in this experiment because the patients are randomly assigned to treatments. (Random assignment does not stop the placebo effect from happening. But including the placebo group means that any difference we observe between the placebo group and the treatment group is due to the treatment.)
- The results of this experiment cannot be trusted because of the placebo effect. (The purpose of the placebo group is to control the influence of the placebo effect. We cannot stop the placebo effect from happening. But including the placebo group means that any difference we observe between the placebo group and the treatment group is due to the treatment.)
- The placebo effect partially explains the results seen in the patients taking the new drug. (We cannot stop the placebo effect from happening. But including the placebo group means that any difference we observe between the placebo group and the treatment group is due to the treatment.)
A: The placebo effect partially explains the results seen in the patients taking the new drug.