Gallup conducts its
polls by telephone, so
people without phones
are always excluded
from the Gallup
sample. In order to
Which of the following is the
best way for Gallup to
correct for the source of bias
described in the previous
problem?
estimate the proportion
of all U.S. adults who
plan to vote in the
upcoming election,
Gallup calls a random
sample of 500 U.S.
adults and constructs a
95% confidence
interval based upon
this sample.
Use a better
○ A.
sampling method.
Select a larger
О в.
sample.
Use a lower
○ C. confidence level,
such as 90%
Use a lower
○ D. confidence level,
such as 99%