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.
Each row of the matrix represents an individual who participated in this study. The rows are comprised of seven features which describe the individual.
There are 1691 paticipants included in this survey.
The first column “sex” is a categorical variable and nominal. The variable “age” is numerical and discrete because it is labeled in increments of one, however age is actually continuous when considering hours, minutes, seconds and so forth. “Marital” is a categorical variable and so is “smoke”, both of these are nominal. “GrossIncome” is a continuous numerical value as it can take on any value. “AmtWeekends”, and “amtWeekdays” are numerical and discrete values because they change in values of one.
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.
The population of interest are all human beings, and the sample consists of 160 children from the age of five to 15.
The study would have a poor correlation to the population as the sample sizes were of children from ages five to 15 as opposed to all ages. However a casual relationship can be established for children in the age range of five to 15. Given a larger sample size, specifically more individuals of all ranges, a more positive correlation can be established for the population being studied.
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.
The generalization that smoking causes dementia later in life seems valid for patients within the generation of 1978-1985 that were 50-60 years old because there is a positive association. However there is no evidence that smoking at an earlier age will also increase your chances of dementia later in life. In addition to these characteristics they volunteered in the exam/survey which may not be representative to the total population. In conclusion, we cannot determine that smoking causes dementia later in life, however, this evidence may justify further studies.
“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 conclusiong made by our friend stating that sleep disorders lead to bullying does not apply because this is an observational study and there are three possible explanations. There is only an association between bullying and sleep disorders (where bullying can cause sleep disorders, sleep disorders can cause bullying, or there is a third variable responsible for both).
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.
Prospective study, information is collected ongoing throughout the experiment.
The treatment group are the subjects assigned to the treatment, exercise, while the control group are the subjects instructed not to exercise.
They make use of blocking because exercise might effect age groups differently, so they equally sample from the three age groups.
No because subjects are aware of the exercise they have to perform.
The experiement does succeed in randomly assigning individuals to the control and treatment groups, however the random sampling is a little bias as it does not include ages below 18 and over 55 therefore it cannot be applied to the population at large. This experiment may show a causal relationship between ages 15 and 55.
Ideally I would extend the age range being studied before funding. I would also like to define exercise, perhaps the treatment groups must reach a heart rate of x beats per minute for y amount of minutes for it to qualify as exercise.
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↩