Statistics Final Exam Questions With Correct Answers
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Course
Statistics
Institution
Statistics
THEBRIGHT EXAM SOLUTIONS 8/20/2024 8:37 PM
Statistics Final Exam Questions With
Correct Answers
A catalog sales company promises to deliver orders placed on the internet within 3 days. Follow-
up calls to a few randomly selected customers show that a 95% confidence interval for the
proportion ...
Statistics Final Exam Questions With
Correct Answers
A catalog sales company promises to deliver orders placed on the internet within 3 days. Follow-
up calls to a few randomly selected customers show that a 95% confidence interval for the
proportion of all orders that arrive on time is 88% +/- 6%. What does this mean? Is this
conclusion correct? Explain.
Between 82% and 94% of all orders arrive on time. - answer✔✔Not correct because this implies
certainty.
A catalog sales company promises to deliver orders placed on the internet within 3 days. Follow-
up calls to a few randomly selected customers show that a 95% confidence interval for the
proportion of all orders that arrive on time is 88% +/- 6%. What does this mean? Is this
conclusion correct? Explain.
95% of all random samples of customers will show that 88% of orders arrive on time. -
answer✔✔Not correct because different samples will give different results.
A catalog sales company promises to deliver orders placed on the internet within 3 days. Follow-
up calls to a few randomly selected customers show that a 95% confidence interval for the
proportion of all orders that arrive on time is 88% +/- 6%. What does this mean? Is this
conclusion correct? Explain.
95% of all random samples of customers will show that 82% to 94% of orders arrive on time. -
answer✔✔Not correct because this is about the population proportion, not the sample proportion
of different samples.
A catalog sales company promises to deliver orders placed on the internet within 3 days. Follow-
up calls to a few randomly selected customers show that a 95% confidence interval for the
proportion of all orders that arrive on time is 88% +/- 6%. What does this mean? Is this
conclusion correct? Explain.
, THEBRIGHT EXAM SOLUTIONS 8/20/2024 8:37 PM
We are 95% sure that between 82% and 94% of the orders placed by the sampled customers
arrive on time. - answer✔✔Not correct because we know that 88% of the orders arrive on time
with a margin of error of 6%.
A catalog sales company promises to deliver orders placed on the internet within 3 days. Follow-
up calls to a few randomly selected customers show that a 95% confidence interval for the
proportion of all orders that arrive on time is 88% +/- 6%. What does this mean? Is this
conclusion correct? Explain.
On 95% of the days, between 82% and 94% of the orders will arrive on time. - answer✔✔Not
correct because the parameter is talking about the interval, not the days.
Several factors are involved in the creation of a confidence interval. Among them are the sample
size, the level of confidence, and the margin of error. Is this statement true?
For a given sample size, higher confidence means smaller margin of error. - answer✔✔False.
Several factors are involved in the creation of a confidence interval. Among them are the sample
size, the level of confidence, and the margin of error. Is this statement true?
For a specified confidence level, larger samples provide smaller margins of error. -
answer✔✔True.
Several factors are involved in the creation of a confidence interval. Among them are the sample
size, the level of confidence, and the margin of error. Is this statement true?
For a fixed margin of error, larger samples provide greater confidence. - answer✔✔True.
Several factors are involved in the creation of a confidence interval. Among them are the sample
size, the level of confidence, and the margin of error. Is this statement true?
For a given confidence level, halving the margin of error requires a sample twice as large. -
answer✔✔False.
What fraction of cars made in Japan? The computer output below summarizes the results of a
random sample of 50 autos. Explain carefully what it tells you.
, THEBRIGHT EXAM SOLUTIONS 8/20/2024 8:37 PM
z-interval for proportion
With 90.00% confidence
0.29938661< P(Japan) < 0.46984416 - answer✔✔On the basis of this sample, we are 90
confident that the proportion of Japanese cars is between 29.9% and 47.0%.
Vitamin D, whether ingested as a dietary supplement or produced naturally when sunlight falls
on the skin, is essential for strong, healthy bones. The bone disease rickets was largely
eliminated in England during the 1950s, but now there is concern that a generation of children
more likely to watch TV or play computer games than spend time outdoors is at increased risk. A
recent study of 2700 children randomly selected from all parts of England found 20% of them
deficient in Vitamin D.
Find a 98% confidence interval. - answer✔✔Z*98= 2.326 (t-table bottom row)
(18.2%, 21.8%)
Vitamin D, whether ingested as a dietary supplement or produced naturally when sunlight falls
on the skin, is essential for strong, healthy bones. The bone disease rickets was largely
eliminated in England during the 1950s, but now there is concern that a generation of children
more likely to watch TV or play computer games than spend time outdoors is at increased risk. A
recent study of 2700 children randomly selected from all parts of England found 20% of them
deficient in Vitamin D.
What does your interval mean? - answer✔✔I am 98% confident that the interval from 18.2% to
21.8% captures the true percentage of English children who are Vitamin D deficient.
Vitamin D, whether ingested as a dietary supplement or produced naturally when sunlight falls
on the skin, is essential for strong, healthy bones. The bone disease rickets was largely
eliminated in England during the 1950s, but now there is concern that a generation of children
more likely to watch TV or play computer games than spend time outdoors is at increased risk. A
recent study of 2700 children randomly selected from all parts of England found 20% of them
deficient in Vitamin D.
What does the "98% confidence" mean? - answer✔✔If we repeat this process over and over
again with a sample size of 2700, we expect that 98% of all intervals to capture the true
population parameter (English children deficient in Vitamin D).
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