1. Intro to Stats and Collecting Data

Notation The control chart for Exercise 1 shows a value of p_bar = 0.0975. What does that value denote, and how is it obtained? What do UCL and LCL indicate?

Reported Versus Measured In a survey of 1046 adults conducted by Bradley Corporation, subjects were asked how often they wash their hands when using a public restroom, and 70% of the respondents said “always.”

a) Identify the sample and the population.

[NW] Television in the Bedroom Is a television (TV) in the bedroom associated with obesity? Researchers questioned 379 twelve-year old adolescents and concluded that the body mass index (BMI) of the adolescents who had a TV in their bedroom was significantly higher than the BMI of those who did not have a TV in their bedroom. Source: Christelle Delmas, Carine Platat, Brigitte Schweitzer, Aline Wagner, Mohamed Oujaa, and Chantal Simon. “Association Between Television in Bedroom and Adiposity Throughout Adolescence,” Obesity, 15:2495–2503, 2007.

d. In the report, the researchers stated, “These results remain significant after adjustment for socioeconomic status.” What does this mean?

Putting It Together: Women, Aspirin, and Heart Attacks In a famous study by the Physicians Health Study Group from Harvard University from the late 1980s, 22,000 healthy male physicians were randomly divided into two groups; half the physicians took aspirin every other day, and the others were given a placebo. Of the physicians in the aspirin group, 104 heart attacks occurred; of the physicians in the placebo group, 189 heart attacks occurred. The results were statistically significant, which led to the advice that males should take an aspirin every other day in the interest of reducing the chance of having a heart attack. Does the same advice apply to women?

In a randomized, placebo-controlled study, 39,876 healthy women 45 years of age or older were randomly divided into two groups. The women in group 1 received 100 mg of aspirin every other day; the women in group 2 received a placebo every other day. The women were monitored for 10 years to determine if they experienced a cardiovascular event (such as heart attack or stroke). Of the 19,934 in the aspirin group, 477 experienced a heart attack. Of the 19,942 women in the placebo group, 522 experienced a heart attack. Source: Paul M. Ridker et al. “A Randomized Trial of Low-Dose Aspirin in the Primary Prevention of Cardiovascular Disease in Women.” New England Journal of Medicine 352:1293–1304.

e. How does randomization deal with the explanatory variables that were not controlled in the study?

Quantitative/Categorical Data Identify each of the following as quantitative data or categorical data

c. The colors of the M&M candies in Data Set 38 “Candies” in Appendix B

Interpreting R^2 For the multiple regression equation given in Exercise 1, we get R^2 = 0.897. What does that value tell us?

In Exercises 29–36, identify what is wrong.

Storks and Babies In the years following the end of World War II, it was found that there was a strong correlation, or association, between the number of human births and the stork population. It therefore follows that storks cause babies.

A(n) ________ design is one in which each experimental unit is randomly assigned to a treatment. A(n) ________ design is one in which the experimental units are paired up.

In Problems 17–20, (a) draw a scatter diagram of the data,

State Populations Currently, California has the largest population with 39,776,830 residents, and Wyoming has the smallest population with 573,520 residents.

d. If we randomly select 50 full-time workers in each of the 50 states, what type of sample is obtained? (random, systematic, convenience, stratified, cluster)

se Notation Using Data Set 1 “Body Data” in Appendix B, if we let the predictor variable x represent heights of males and let the response variable y represent weights of males, the sample of 153 heights and weights results in se = 16.27555 cm. In your own words, describe what that value of se represents.

Sampling Method Assume that the population consists of all students currently in your statistics class. Describe how to obtain a sample of six students so that the result is a sample of the given type.

d. Cluster sample

"Cellolar Phones Researchers wanted to determine whether there is an association between mobile phone use and body mass index. To do so, 105,028 men and women aged 18 years or over from the United Kingdom were recruited and their cell-phone use behavior was studied (number of calls per day, number of hours per week, year cell phone was first used) along with other variables (amount of exercise, body mass index) of the individuals. The researchers found a strong positive association between duration of phone calls on a cell phone and body mass index (that is, as the duration of phone calls increases, body mass index tends to increase as well).

Many studies involving cell phones look for a link between cell-phone usage and negative health outcomes (such as stroke or cancer) due to radio-frequency exposure. The following quote is from the article: “Obesity is associated with health outcomes such as stroke and cancers, which are of interest in relation to radio frequency exposure, and therefore is potential for confounding.” Explain what this means."

In Exercises 21–28, determine whether the study is an experiment or an observational study, and then identify a major problem with the study.

Atkins Weight Loss Program An independent researcher tested the effectiveness of the Atkins weight loss program by randomly selecting 1000 subjects using that program. Each of the subjects was called to report their weight before the diet and after the diet.

Smoker’s IQ A study was conducted in which 20,211 18-year-old Israeli male military recruits were given an exam to measure IQ. In addition, the recruits were asked to disclose their smoking status. An individual was considered a smoker if he smoked at least one cigarette per day. The goal of the study was to determine whether adolescents aged 18 to 21 who smoke have a lower IQ than nonsmokers. It was found that the average IQ of the smokers was 94, while the average IQ of the nonsmokers was 101. The researchers concluded that lower IQ individuals are more likely to choose to smoke, not that smoking makes people less intelligent.

What is the research objective?