Question

1. In a simple random sample of 144 households in a county in Virginia, the average number of children in these households was 3.62 children. The standard deviation from this sample was 2.40 children. A member of the county government thinks that 90% confidence isn't enough. He wants to be 99% confident.

Another member of the county government is satisfied with 90% confidence , but she wants a smaller margin of error. How can we get a smaller margin of error, still with 90% confidence ?

a. Take a larger sample, because larger samples result in smaller margins of error.

b. Take another sample of the same size and you might be lucky and get a much smaller margin of error.

c. Take a sample of adults from a neighborhood in the county instead of from the entire county. Then, the population will be smaller which will give a smaller margin of error.

d. Carry out a call-in poll to get a voluntary response sample. Voluntary response samples have no margin of error.

e. Take a smaller sample, because smaller samples result in smaller margins of error.

2. The phrase "95% confidence" in a confidence statement means that

a. the results are true for 95% of the population.

b. 95% of the population falls within the announced margin of error.

c. the results were obtained using a method that gives correct answers in 95% of all samples.

d. the probability is 0.95 that a randomly chosen individual's value falls within the announced margin of error.

Answer #1

TOPIC:Confidence interval.

A simple random sample with
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(a)
Develop a 90% confidence interval for the population mean.
to
(b)
Develop a 95% confidence interval for the population mean.
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(c)
Develop a 99% confidence interval for the population mean.
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