For Exercise 8.1, see page 168; for Exercise 8.2, see page 174.
8.3 Comparing marijuana use. According to the 2011–2012 National Survey on Drug Use and Health, among young adults aged 18–25 years, approximately 29.2% of young adults in Arizona, approximately 34.4% of young adults in Michigan, and approximately 30.4% of young adults in Virginia used marijuana in the past year. Which of the following is true?
(a) We cannot use these percentages to compare marijuana use by young adults in these states because we do not know how many young adults used marijuana in the past year in each state.
(b) We cannot use these percentages to compare marijuana use by young adults in these states because we do not know how many young adults live in each state.
(c) We can use these percentages to compare marijuana use by young adults in these states because we are given rates.
(d) None of the above is true.
8.4 What is the instrument of measurement? A college president is interested in student satisfaction with recreational facilities on campus. A questionnaire is sent to all students and asks them to rate their satisfaction on a scale of 1 to 5 (with 5 being the best). The instrument of measurement is
(a) a student.
(b) the questionnaire.
(c) the rating on the scale.
(d) satisfaction.
8.5 Weight at the doctor’s office. When you visit the doctor’s office, several measurements may be taken, one of which is your weight. A doctor’s office encourages patients to keep their shoes on to be weighed and promises to subtract 2 pounds for the weight of the patient’s shoes. Which of the following is true once the patient’s weight is adjusted by 2 pounds?
(a) This will be a reliable measure of the patient’s weight.
(b) This will be a valid measure of the patient’s weight.
(c) This will be an unbiased measure of the patient’s weight.
(d) None of the above is true.
8.6 Measuring athletic ability. Which of the following is not a valid measurement of athletic ability?
(a) Time (in seconds) to run a 100-meter dash
(b) Number of times a person goes to the gym per week
(c) Maximum weight (in pounds) a person can bench-press
(d) Number of sit-ups a person can do in one minute
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8.7 Comparing teaching assistants (TAs). Professor Holmes has two teaching assistants who grade homework for a Statistics 101 course. Professor Holmes gives each of the two teaching assistants a rubric (a clear scoring guide) for the TAs to use when they grade the assignments. Holmes gives each TA the same student’s paper to grade and has each TA grade the paper according to the rubric. Professor Holmes is doing this to try to guarantee the scores given by the TAs are
(a) not biased.
(b) predictive.
(c) reliable.
(d) valid.