CH 4
1) Patients who visit a clinic to help them stop smoking are given a choice of two treatments:
undergoing hypnosis or applying nicotine patches. The percentages who quit smoking are
compared for the two methods. Is this study a survey, an experiment, an observational study, or a
case study? Explain your reasoning.
●This study is an experiment because it measures the effect of manipulation, and in this
case it is the two treatments given to the patients. In experiments you measure the cause
and effect and that is what this study is measuring. You measure the result of the feature
being manipulated, which is the two treatments on the percentages who quit smoking.
11) The Sacramento Bee (11 Feb. 2001, p. A20) reported on a Newsweek poll that was based on
interviews with 1000 adults, asking questions about a variety of issues. a. What is the margin of
error for this poll? b. One of the statements in the news story was “a margin of error of plus or
minus three percentage points means that the 43 percent of Americans for and the 48 percent of
Americans against oil exploration in Alaska’s Arctic National Wildlife Refuge are in a statistical
dead heat.” Explain what is meant by this statement.
●A. The margin of error for this poll is 3.16%.
●B. This means that between 40 and 46% are the Americans in favor of oil exploration,
and for those against oil exploration are the Americans between 45 and 51%. Since it is
plus or minus three percentage points, you just add and subtract from 43 and 48.
23)What role does natural variability play when trying to determine the population average of a
measurement variable from a sample? (Hint: Read the section on stratified sampling.)
●The accuracy of the measurements of a population all depends on the natural variability
of those measurements. The less variability there is, the more precise you can determine
the population average of the sample. With more variability however, it is more difficult
to determine the differences and average of a population.
32)Suppose that a gourmet food magazine wants to know how its readers feel about serving beer
with various types of food. The magazine sends surveys to 1000 randomly selected readers.
Explain which one of the “difficulties and disasters” in sampling the magazine is most likely to
face
●One of the difficulties that the gourmet food magazine is most likely to face is having a
low response rate. Since this is a voluntary survey, it is possible that only those who have
a strong opinion on this are most likely to respond. Which leads the results to be less
likely generalized to the population as a whole.
CH 5
