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 “\(\pounds\)” 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?
  2. How many participants were included in the survey?
  3. 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.
## [1] "(a) Each row represents to each participant"
## [1] "(b) Total of 1691 participants were surveyed"
## [1] "(c) Sex - Categorical, Age - Numerical discrete, Martial - Categorical, Gross income - Categorical ordinal, Smoke - Categorical, Amount weekends/ weekdays - Numerical continuous"

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.
  2. 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.
## [1] "(a) Population of interest is children of age group between 5 and 15. The sample is 160"
## [1] "(b) We cannot generalize this study to the pouplation since the sample was not random. We can use this study to establish causal relationship as it was an experimental study."

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.

## [1] "We cannot conclude from this study since the sample is not random, participants voluntarily participated. Causation can only be inferred from random sample. We can draw an association between smoking habits and dementia"
  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?

## [1] "We cannot justify from this study since its a observation rather than an experimental study. We can draw an association between bullying and sleep disorders"

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?
  2. What are the treatment and control groups in this study?
  3. Does this study make use of blocking? If so, what is the blocking variable?
  4. Does this study make use of blinding?
  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.
  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?
## [1] "(a) This is an Experimental study"
## [1] "(b) Treatment - group that is told to exercise. Control - group that is told not to exercise"
## [1] "(c) Yes this study uses blocking. Age - is the blocking variable"
## [1] "(d) No, study doesn't use blinding. Participants know they are in exercise group or non-exercise group"
## [1] "(e) We can use this study to establish causal relationship between exercise and mental health since it was experimented on a random sample. Conclusions can be generalized since a wider age group of population was included."
## [1] "(f) Reservations I would have interms of selecting participants in the groups like if an active exercising person is put in a control group. This would impact the study."

  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↩︎