Chapter 4: Q 40. (page 230)
When we take a census, we attempt to collect data from
(a) a stratified random sample.
(b) every individual selected in an SRS.
(c) every individual in the population.
(d) a voluntary response sample.
(e) a convenience sample.
The correct option is (c) every individual in the population.
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Checking for bias Comment on each of the following as a potential sample survey question. Is the question clear? Is it slanted toward the desired response?
(a) Which of the following best represents your opinion on gun control?
1. The government should confiscate our guns.
2. We have the right to keep and bear arms.
(b) A freeze on nuclear weapons should be favored because it would begin a much-needed process to stop everyone in the world from building nuclear
weapons now and reduce the possibility of nuclear war in the future. Do you agree or disagree?
Technology for teaching statistics The Brigham Young University (BYU) statistics department is performing experiments to compare teaching methods. Response variables include students’ final-exam scores and a measure of their attitude toward statistics. One study compares two levels of technology for large
lectures: standard (overhead projectors and chalk) and multimedia. There are eight lecture sections of a basic statistics course at BYU, each with about students. There are four instructors, each of whom teaches two sections. Suppose the sections and lecturers are as follows:
(a) Suppose we randomly assign two lecturers to use standard technology in their sections and the other two lecturers to use multimedia technology. Explain how this could lead to confounding.
(b) Describe a better design for this experiment.
Who goes to the convention? A club has student members and faculty members. The students are
The club can send students and faculty members to a convention. It decides to choose those who will go by random selection. How will you label the two strata? Use Table D, beginning at line to choose a stratified random sample of students and faculty members.
Sleep debt A researcher reported that the average teenager needs 9.3 hours of sleep per night but gets only hours.By the end of a -day school week, a teenager would accumulate about 15 hours of “sleep debt.” Students in a high school statistics class were skeptical, so they gathered data on the amount of sleep debt (in hours) accumulated over time (in days) by a random sample of high school students. The resulting least-squares regression equation for their data is . Do the students have reason to be skeptical of the research study’s reported results? Explain.
In an interesting experiment, researchers examined the effect of ultrasound on birth weight. Pregnant women participating in the study were randomly assigned to one of two groups. The first group of women received an ultrasound; the second group did not. When the subjects’ babies were born, their birth weights were recorded. The women who received the ultrasounds had heavier babies.
Did the experimental design take the placebo effect into account? Why is this important?
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