1. Intro to Stats and Collecting Data

Define each of the following. Confounding

Determine the level of measurement of the data set. Explain.

The total compensations (in millions of dollars) of the ten highest-paid CEOs at U.S. public companies are listed. (Source: 24/7 Wall St.)

280.6 66.9 42.9 36.5 34.3 31.6 31.6 28.8 26.4 25.8

Exercises 5–8 refer to the study of an association between which ear is used for cell phone calls and whether the subject is left-handed or right-handed. The study is reported in “Hemispheric Dominance and Cell Phone Use,” by Seidman et al., JAMA Otolaryngology—Head & Neck Surgery, Vol. 139, No. 5. The study began with a survey e-mailed to 5000 people belonging to an otology online group, and 717 surveys were returned. (Otology relates to the ear and hearing.)

Experiment or Observational Study Is the study an experiment or an observational study? Explain.

Obtaining a Systematic Sample A quality-control engineer wants to be sure that bolts coming off an assembly line are within prescribed tolerances. He wants to conduct a systematic sample by selecting every 9th bolt to come off the assembly line. The machine produces 30,000 bolts per day, and the engineer wants a sample of 32 bolts. Which bolts will be sampled?

The age of a person is commonly considered to be a continuous random variable. Could it be considered a discrete random variable instead? Explain.

A study showed an association between intentional weight loss and a decreased risk of high blood pressure. Is it appropriate to infer from this study that weight loss causes a decreased risk of high blood pressure? Explain. (Source: European Association for the Study of Obesity)

Simple Random Sample vs. Random Sample Refer to the definition of simple random sample here and its accompanying definition of random sample enclosed within parentheses. Determine whether each of the following is a simple random sample and a random sample.

a. In Major League Baseball, there are 30 teams, each with an active roster of 25 players. The names of the teams are printed on 30 separate index cards, the cards are shuffled, and one card is drawn. The sample consists of the 25 players on the active roster of the selected team.

a

Notation The author conducted an experiment in which the height of each student was measured in centimeters and those heights were matched with the same students’ scores on the first statistics test.

b. Without doing any research or calculations, estimate the value of r.

Types of Data In each of the following, identify the level of measurement of the sample data (nominal, ordinal, interval, ratio) and the type of sampling used to obtain the data (random, systematic, convenience, stratified, cluster).

b. In each of the 50 states, 50 voters are randomly selected and their political party affiliations are identified.

In Exercises 5–12, identify whether the given value is a statistic or a parameter.

Smart Phones In a Pew Research Center poll, a sample of adults in the United States was obtained, and it was found that 72% of them own smart phones.

Determine whether the data are qualitative or quantitative. Explain your reasoning.

Response times for a customer service representative

Platelet-Rich Plasma Does a platelet-rich plasma (PRP) injection into the scalp promote hair growth? Researchers identified 30 female patients with female pattern hair loss. The patients ranged in age from 20 to 45 years. For each patient, two areas with hair loss were identified. A coin toss was used to decide which area received the PRP injection and which received a saline injection. Injections were given to each patient at one-week intervals. After 6 months the change in the patients’ hair density (number of hairs per square centimeter) and hair diameter (millimeters) was measured. The mean difference in hair density (PCP minus saline) was 59.47 hairs/cm2 and the mean difference in hair thickness was 0.08 mm.

What type of experimental design is this?

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

b. What is the level of measurement for the numbers of residents in the different states? (nominal, ordinal, interval, ratio)

In Exercises 33–36, identify which of these designs is most appropriate for the given experiment: completely randomized design, randomized block design, or matched pairs design.

West Nile Vaccine Currently, there is no approved vaccine for the prevention of infection by West Nile virus. A clinical trial of a possible vaccine is being planned to include subjects treated with the vaccine while other subjects are given a placebo.