A New York Times article from October 9, 2003, contains this explanation about an exit survey for a California recall election: In theory, in 19 cases out of 20, the results from such polls should differ by no more than plus or minus two percentage points from what would have been obtained by seeking to interview everyone who cast a ballot in the recall election. Assume a simple random sample and P= .54. How big was n? An erstwhile commercial claimed that "Four out of five dentists surveyed would recommend Trident for their patients who chew gum." Assume the results were based on a random sample from the population of all dentists. Find a 90% confidence interval for the true proportion if the sample size was n=5. Repeat with n=100 and n=1,000. A survey is taken of 250 students, and a P of 0.45 is found. The same survey is repeated with 1,000 students, and the same value is found. Compare the two 95% confidence intervals. What is the relationship? Is the margin of error for the second one four times smaller? How much smaller is it?
A New York Times article from October 9, 2003, contains this explanation about an
exit survey for a California recall election:
In theory, in 19 cases out of 20, the results from such polls should differ
by no more than plus or minus two percentage points from what would
have been obtained by seeking to interview everyone who cast a ballot in
the recall election.
Assume a simple random sample and P= .54. How big was n?
An erstwhile commercial claimed that "Four out of five dentists surveyed would
recommend Trident for their patients who chew gum."
Assume the results were based on a random sample from the population of all dentists.
Find a 90% confidence interval for the true proportion if the
with n=100 and n=1,000.
A survey is taken of 250 students, and a P of 0.45 is found. The same survey is
repeated with 1,000 students, and the same value is found. Compare the two 95%
confidence intervals. What is the relationship? Is the margin of error for the second one
four times smaller? How much smaller is it?
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