R Markdown

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.

  1. What does each row of the data matrix represent?

    It reprsent each participatent’s smoking habits.

  2. How many participants were included in the survey?

    Total 1691 participants

  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.

    index: numerical continuous

    sex: categorical nominal

    age: numerical discrete

    marital: categorical nominal

    grossIncome: categorical ordinal

    smoke: categorical nominal

    amtWeekends: numerical discrete

    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 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.

  1. Identify the population of interest and the sample in this study.

    160 children between the ages of 5 and 15.

  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.

The study can’t establish causal relationship because we don’t know whether those 160 children are randomly choose. This is an observation 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.

No. We can’t get the conclusion because the 23,123 smokers are chosen from health plan, instead of random population. In addition, we don’t know whether there are other reasons to cause the Dementia. No experiment is involved.

  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?

This statement is not justified. This is an observation but not an experiment. We don’t know whether those behavioral concerns are based on those children who have sleep disorders or randomly chosen from all the children. In addition, they might have other reasons to cause the behavior issues, such as lack of attention. If we can’t exclude other reasons base on a fair experiment, we can’t draw any conclusion.

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?

Randomized experiment.

  1. What are the treatment and control groups in this study?

Treatment group: group that excercising twice a week. Control group: group not excercising at all.

  1. Does this study make use of blocking? If so, what is the blocking variable?

Yes. They group people base on age.

  1. Does this study make use of blinding?

Base on the information provide, the experiment doesn’t use blinding. One group aware they will do exercise twice a week and the other group instruct not to exercise.

  1. 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.

We can establish a causal relationship if the data size is large enough because the example is randomly chosen. The only concern is whether the actively exercise person before was chose to not exercise at all.

  1. Suppose you are given the task of determining if this proposed study should get funding. Would you have any reservations about the study proposal?

As I mention before, my only reservation about the study is the morality of forcing those actively exercising person to stop exercising. In addition, we don’t know how long the experiment is and it might affect our study due to those people’s emotion change.