Smoking habits of UK residents. (1.10, p. 20) A survey was conducted to study the smoking habits of UK residents. Below is a data matrix displaying a portion of the data collected in this survey. Note that “£” stands for British Pounds Sterling, “cig” stands for cigarettes, and “N/A” refers to a missing component of the data.

  1. What does each row of the data matrix represent?

Solution: Each row of the data represent UK resident.

  1. How many participants were included in the survey?

Solution: There are 1691 participants in the survey

  1. Indicate whether each variable in the study is numerical or categorical. If numerical, identify as continuous or discrete. If categorical, indicate if the variable is ordinal.

Solution: Gender Caegorical with 2 factor level Age Numerical MaritalStatus Categorical HighestQualification Categorical Nationality Categorical Ethnicity Categorical GrossIncome Categorical Region Categorical Smoke Categorical AmtWeekends Numerical AmtWeekdays Numerical Type Categorical

Cheaters, scope of inference. (1.14, p. 29) Exercise 1.5 introduces a study where researchers studying the relationship between honesty, age, and self-control conducted an experiment on 160 children between the ages of 5 and 151. The researchers asked each child to toss a fair coin in private and to record the outcome (white or black) on a paper sheet, and said they would only reward children who report white. Half the students were explicitly told not to cheat and the others were not given any explicit instructions. Differences were observed in the cheating rates in the instruction and no instruction groups, as well as some differences across children’s characteristics within each group.

  1. Identify the population of interest and the sample in this study.

Solution: The sample consist of 160 children between the ages of 5 to 15.

  1. Comment on whether or not the results of the study can be generalized to the population, and if the findings of the study can be used to establish causal relationships.

Solution: The study seems to find causal relationship, but result of the study may not be generalized because the samle size is small.

Reading the paper. (1.28, p. 31) Below are excerpts from two articles published in the NY Times:

  1. An article titled Risks: Smokers Found More Prone to Dementia states the following:

“Researchers analyzed data from 23,123 health plan members who participated in a voluntary exam and health behavior survey from 1978 to 1985, when they were 50-60 years old. 23 years later, about 25% of the group had dementia, including 1,136 with Alzheimer’s disease and 416 with vascular dementia. After adjusting for other factors, the researchers concluded that pack-a- day smokers were 37% more likely than nonsmokers to develop dementia, and the risks went up with increased smoking; 44% for one to two packs a day; and twice the risk for more than two packs.”

Based on this study, can we conclude that smoking causes dementia later in life? Explain your reasoning.

Solution: It is difficult to infer causation from this observational study. Experimental study with treatment and control group may be more appropriate to infer causation. However, there is an association between smoking and these diseases.

  1. Another article titled The School Bully Is Sleepy states the following:

“The University of Michigan study, collected survey data from parents on each child’s sleep habits and asked both parents and teachers to assess behavioral concerns. About a third of the students studied were identified by parents or teachers as having problems with disruptive behavior or bullying. The researchers found that children who had behavioral issues and those who were identified as bullies were twice as likely to have shown symptoms of sleep disorders.”

A friend of yours who read the article says, “The study shows that sleep disorders lead to bullying in school children.” Is this statement justified? If not, how best can you describe the conclusion that can be drawn from this study?

Solution:

This statement cannot be justified simply on the outcome of this observational study.

Exercise and mental health. (1.34, p. 35) A researcher is interested in the effects of exercise on mental health and he proposes the following study: Use stratified random sampling to ensure rep- resentative proportions of 18-30, 31-40 and 41-55 year olds from the population. Next, randomly assign half the subjects from each age group to exercise twice a week, and instruct the rest not to exercise. Conduct a mental health exam at the beginning and at the end of the study, and compare the results.

  1. What type of study is this? Solution: Experimental Study

  2. What are the treatment and control groups in this study? Solution: The treatment group is half of the participants excercising twice a week. The control group is half of the participants not excercising.

  3. Does this study make use of blocking? If so, what is the blocking variable? Solution: The treatment uses block of Age group. The Age blocks are 18-30 year olds, 31-40 year olds and 41-55year olds.

  4. Does this study make use of blinding? Solution: This is not a blind study as the participants knew the group they belong, that is the exercises group or the none exercise group.

  5. Comment on whether or not the results of the study can be used to establish a causal rela- tionship between exercise and mental health, and indicate whether or not the conclusions can be generalized to the population at large. Solution: Causal relational may be possible to generalize but the study is still limited to generalize on a larger population.

  6. Suppose you are given the task of determining if this proposed study should get funding. Would you have any reservations about the study proposal? Solution: No. I will support funding the study and recommend a larger sample size.

  1. Alessandro Bucciol and Marco Piovesan. “Luck or cheating? A field experiment on honesty with children”. In: Journal of Economic Psychology 32.1 (2011), pp. 73–78. Available at https://papers.ssrn.com/sol3/papers.cfm?abstract_id=1307694↩