In: Statistics and Probability
A restaurant wants to estimate the average bill paid by a party
of two for dinner...
A restaurant wants to estimate the average bill paid by a party
of two for dinner (service hours after 5 p.m.) They take a random
sample of 100 bills and find that they average $80 with a standard
deviation of $40. In making an 80% confidence interval for the
parameter of interest, they should get a margin of error of
about
A random sample of 900 homeowners in Centre County is taken in
order to estimate the average amount of money spent by homeowners
on landscaping this spring. It turns out that this group spent an
average of $200 with a standard deviation of $150. A 95% confidence
interval for the average amount spent on landscaping by all Centre
County homeowners is calculated to be $200 ± $10. Which is true
about this situation?
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The true average amount spent must be in this interval. |
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The procedure used here produces intervals that cover the right
answer for 95% of all samples. |
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This confidence interval won’t cover the right answer since a
histogram of the amount spent is skewed. |
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The interval would be larger if we used an 80% confidence level
instead of 95%. |
Two polls about the President’s policy for the War in Syria used
the same methodology and had the same sample size but had different
question wording. In the first poll 45% of those surveyed favored
the policy, while in the second poll 55% favored the policy.
True or False: even though the question wording might have
changed the results, it would not have any affect on the
margin-of-error.