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Chapter 8: Q 2. (page 506)
Got shoes? The class in Exercise 1 wants to estimate the variability in the number of pairs
of shoes that female students have by estimating the population standard deviation .
The standard deviation is
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In a poll conducted by phone,
I. Some people refused to answer questions.
II. People without telephones could not be in the sample.
III. Some people never answered the phone in several calls.
Which of these possible sources of bias is included in the margin of error announced for the poll?
a. I only
b. II only
c. III only
d. I, II, and III
e. None of these
We love football! A Gallup poll conducted telephone interviews with a random sample of adults aged 18 and older. Data were obtained for 1000 people. Of these, 370 said that football is their favorite sport to watch on television.
a. Define the parameter p in this setting.
b. What point estimator will you use to estimate p? What is the value of the point estimate?
c. Do you believe that the value of the point estimate is equal to the value of p? Explain your answer.
Engine parts A random sample of 16 of the more than auto engine crankshafts produced in one day was selected. Here are measurements (in millimeters) of a critical component on these crankshafts:
a. Construct and interpret a confidence interval for the mean length of this component on all the crankshafts produced on that day.
b. The mean length is supposed to be mm but can drift away from this target during production. Does your interval from part (a) suggest that the mean has drifted from mm? Explain your answer.
Blood pressure A medical study finds that and
for the seated systolic blood pressure of the randomly selected adults. What is the standard error of the mean? Interpret this value in context.
A Gallup poll found that only of American adults expect to inherit money or valuable possessions from a relative. The poll鈥檚 margin of error was 卤3 percentage points at a confidence level. This means that
a. the poll used a method that gets an answer within 3% of the truth about the population of the time.
b. the percent of all adults who expect an inheritance must be between and .
c. if Gallup takes another poll on this issue, the results of the second poll will lie between and .
d. there鈥檚 a 95% chance that the percent of all adults who expect an inheritance is between
25% and 31%.
e. Gallup can be 95% confident that between 25% and 31% of the sample expect an inheritance.
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