BackStandard Deviation One way to get a very rough approximation of the value of a standard deviation of sample data is to find the range, then divide it by 4. The range is the difference between the highest sample value and the lowest sample value. In using this approach, what value is obtained from the sample data listed in Exercise 1 “IQ Scores”?
Determine whether the statement is true or false. If it is false, rewrite it as a true statement.
A sample statistic will not change from sample to sample.
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.
Bull Markets A bull market is defined as a market condition in which the price of a security rises for an extended period of time. A bull market in the stock market is often defined as a condition in which a market rises by 20% or more without a 20% decline. The data to the right represent the number of months and percentage change in the S&P 500 (a group of 500 stocks) during the 25 bull markets dating back to 1929 (the year of the famous market crash).
a. Treating the length of the bull market as the explanatory variable, draw a scatter diagram of the data.
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