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 of the matrix represents and individual with their demographic data (sex, age, marital status, income), smoking behavior (during the week, and on weekends, type ) and the region they live in. I loaded the data and you get different answers. There are more colums in the xls file.
- How many participants were included in the survey?
1693 observations were included in the data. I loaded the data and you get different answers. There are more rows in the xls file (1693 vs 1691-last row in the table).
- 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/nominal
Age - numerical/continuous
Marital Status - categorical/nominal
Highest Qualifications - categorical/ordinal
Nationality - categorical/nominal
Ethnicity - categorical/nominal
Gross Income - categorical/ordinal
Region - categorical/nominal
Smoke? - categorical/nominal
Amount Weekends - numerical/continuous
Amount Weekdays - numerical/continuous
Type - categorical/nominal
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 15. 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.
- Identify the population of interest and the sample in this study.
population of interest: children between the ages of 5 and 15
the sample population was 160 children between the ages of 5 and 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.
yes the findings from the sample group can be generalized to the population if the sample group of 160 children is a representation of the broader population
yes the findings of the study could be used to establish a causal relationship
Reading the paper. (1.28, p. 31) Below are excerpts from two articles published in the NY Times:
- 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.
Yes potentially - the researcher observed an association between smoking and dementia later in life. It also states that the analysis controlled for other factors that could be impacting the observations. So depending on how well the researcher controlled for other factors then we could say that the study proves the hypothesis.
- 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?
no - the study finds an association between sleep disorders and bullying behaviors. It however does not assert the existence or direction of causality. The summary never states if bullying is the explanatory variable or a sleeping disorder is the explanatory variable. Also this was an observational study and thus did not include the necessary elements to prove causality (random assignments to a treatment and control group)
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.
- What type of study is this?
experiment
- What are the treatment and control groups in this study?
treatment group - half the population of each category (18-30, 31-40 & 41-55) that was instructed to exercise twice a week
control - half the population of each category (18-30, 31-40 & 41-55) that was instructed not to exercise
- Does this study make use of blocking? If so, what is the blocking variable?
no the grouping of study participants is an example of stratified sampling
- Does this study make use of blinding?
no the treatment group and the treatments are clearly observable
- 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.
yes - the study is an experiment that includes random assignment of subjects to either a treatment or control group and the mental health of treatment / control subjects is measured before and after the treatment period
- Suppose you are given the task of determining if this proposed study should get funding. Would you have any reservations about the study proposal?
Not based on the write-up provided. There is no indication of duration of study. It might require months or years to for exercise to impact mental health. The study only includes one frequency of exercise (would more frequent exercise change the results) and it will be difficult to ensure compliance (exercise when they are supposed to and refrain from exercise for the duration of the experiment).