‘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.’
What does each row of the data matrix represent? ‘Each row contains social status on every particpant: sex, age, marital status, gross income, smoke Y/N, quantity per week.’
How many participants were included in the survey? ‘1691 total participants.’
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. ’ Sex: categorical , non-ordinal variable Age: numerical variable Marital: categorical, non-ordinal variable Gross Income: numerical variable Smoke: categorical Amount on Weekends: numerical variable Amount on Weekdays: numerical variable ’
’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 childrens characteristics within each group.’
Identify the population of interest and the sample in this study. ‘The population of interest are children, in which there is a sample of 160, aged 5-15.’
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. ‘The results of this study cannot necessarily be generalized because there is no indication in the description of the that tells where the participants are coming from. The reader does not know if they are all from the same town, region, or country. Randomness does not seem to be a factor according to the description.’
Reading the paper. (1.28, p. 31) Below are excerpts from two articles published in the NY Times:
“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.
‘Based on this excerpt, we cannot conclude that smoking causes later in life because the group surveryed ranged from 50-60 years initially, and then were evaluated 23 years later. The sample was not randomized among smokers.’
“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?’
The statement about the article is not justified simply because correlation is not causation, especially at face value. The friend also does not expand on his claim by going into detail of what the article had to say.
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.
4a) This is a case control study.
4b) The treatment group is the group told to exercise twice a week, and the control group are the ones not exercising.
4c) Yes, blocking is used during this study, and the age of the participants is the blocked variable.
4d) Blinding is not mentioned in the description of the study, thus we cannot confirm nor deny if blinding was used
4e) The results of the study can be used to establish a correlation relationship between mental health and exercising. Because the sampling that was used is stratified, I believe this can be applied to the population at large.
4f) This proposal does not seem elaborate nor specific enough to seek funding. I think more details should be mentioned and planned in order to get more effective and productive results. As the reader, I do not feel convinced we had a true control group. I would like to see more details of the study before considering funding for this type of research.
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↩︎