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.
Answer: Each row represent one UK resident and his/her somking habits.
Answer: There were 1691 participants included in the survey.
Answer: The classification of each variable is as below: 1)Sex: Categorical - Nomial; 2)Age:Numerical - Continuous; 3)Marital:Categorical - Nomial; 4)GrossIncome: Categorical - Ordinal; 5)Smoke:Categorical - Nomial; 6)AmtWeekends: Numerical - Discrete; 7)AmtWeekdays: Numerical - Discrete.
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.
Answer: 1) The population of interest is all children between the ages of 6 and 15. 2) The samle is 160 children in above scope.
Answer: 1) The methodology of sampling is the key to this question. If the sample is representative and unbiased then the study can be generalized to the population, vise versa. The sample of 160 children in this study is too small to represent the all children in ages of 6 to 15. Therefore the results can not be generalized to the population. 2) This is a experimental study, which can be used to establish causal relationships. Half of the children are told not to cheat, therefore the difference of the behavior between the two groups of children are causally related to the test operator’s experimental interference.
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.
Answer: We conclude that smoking causes dementia later in life based on this study. Firstly, this is a observational study, in which association between smoking and dementia can be revealed. However association does not imply causation. Therefore this study does not imply smoking cases dementia.
“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?
Answer: This statement is not justified. This is a observational study. The study shows there is association between sleep disordersand bullying/behavioral issues. The conclusion is better to be: children who have problems with disruptive behavior or bullying are more likely to have symptons of 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.
Answer: This is an blocking randomized experimental study.
Answer: The treatment group is half of the samples from each age segment 18-30, 31-40 and 41-55 years old and are assigned to exercise twice a week; The control groups are the other half of the samples from each age segment 18-30, 31-40 and 41-55 years hold and are instructed not to exercise.
Answer: Yes, this study make use of blocking. The blokcing variable is age. The researcher use stratified random sampling to collect samples from age groups 18-30,31-40 and 41-55.
Anwer: No, this study does not make use of blinding. The objects in the study are clearly instructed to execise or not to execise. No placebo is used in this experiment.
Answer: 1) Yes, the results of the study can be used to establish a causal relationship between exercise and mental health because this is an experimental study. 2) Yes, the conculsions of the study can be generalized to the population at large because the researcher use stratified random sampling to ensure representative proportions of each target age groups from the population.
Answer: Mental health is a complicated subject, it can possibly be associated multiple factors. Therefore to admit for funding, I will put more restriction on sample collection including profession, physical health status, marital status etc., to analysis possible noise effect by unknown factors. Exercise will be quantitatively instructed and measured in stead of ‘twice a week’ for treatment groups. Also participants’ will be closely monitored to ensure quality of response.
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↩