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Vickyhung Vickyhung
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Posts: 567
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3 years ago
Which of the following statements is true regarding a 95 confidence interval? Assume numerous large samples are taken from the population.
 a. In 95 of all samples, the sample proportion will fall within 2 standard deviations of the mean, which is the true proportion for the population.
  b. In 95 of all samples, the true proportion will fall within 2 standard deviations of the sample proportion.
  c. If we add and subtract 2 standard deviations to/from the sample proportion, in 95 of all cases we will have captured the true population proportion.
  d. All of the above.

Q. 2

The formula for calculating a confidence interval for a population proportion is based on the rule of sample proportions, which has assumptions that need to be met. What is the most important assumption that you need to check before applying the confidence interval formula to a sample proportion?

Q. 3

Using one divided by the square root of the sample size is known as a conservative' formula for the margin of error for a sample proportion. Explain what that means.

Q. 4

It is often the case that the amount of data available does not allow us to conclusively detect a significant relationship or effect with a confidence interval. That __________ (choose: does, does not) mean that no important relationship or effect exists in the population.
 Fill in the blank(s) with correct word

Q. 5

It__________ (choose: is, is not) numerically possible for a confidence interval for a proportion to fall below zero.
 Fill in the blank(s) with correct word

Q. 6

Suppose the U.S. government reports that the total number of people in the U.S. who are currently infected with HIV is likely to be between 300,000 and 1,000,000 . What is the margin of error for these findings? (Assume a symmetric 95 confidence interval.)
 a. +/ 350,000
  b. +/ 700,000
  c. +/ 5
  d. Not enough information to tell

Q. 7

Suppose a survey was conducted to find out what proportion of Americans intend to vote in the next Presidential election. For which of the following confidence intervals would it be fair to conclude, with high confidence, that a majority of Americans will vote in the next Presidential election?
 a. 52 plus or minus 3
  b. 52 plus or minus 2
  c. 52 plus or minus 1
  d. All of the above are too close to call..

Q. 8

Name one possible problem that could occur in a survey to make what is reported to be a narrow 95 confidence interval a meaningless result.

Q. 9

Which would be wider, a 90 confidence interval or a 95 confidence interval? (Assume both of them were calculated using the same sample data.) Explain your answer.
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Answer verified by a subject expert
AsteriaAsteria
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Posts: 304
Rep: 3 0
3 years ago
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Answer to #1

D

Answer to #2

THE SAMPLE SIZE MUST BE LARGE ENOUGH SO THAT YOU ARE LIKELY TO SEE AT LEAST FIVE OF EACH OF THE TWO POSSIBLE RESPONSES OR OUTCOMES.

Answer to #3

THE TRUE MARGIN OF ERROR FOUND BY THE FORMULA 2  (S.D.) IS ALWAYS LESS THAN OR EQUAL TO THIS VALUE. IT IS EQUAL WHEN THE PROPORTION USED IN THE FORMULA FOR S.D. IS .50 .

Answer to #4

DOES NOT

Answer to #5

IS

Answer to #6

A

Answer to #7

C

Answer to #8

ANY REASONABLE ANSWER OK. EXAMPLES: BIAS OF ANY KIND; A NON-RANDOM SAMPLE; MISLEADING WORDING OF QUESTIONS; ETC.

Answer to #9

THE 95 CONFIDENCE INTERVAL IS WIDER. SINCE THE DATA SAMPLE SIZE IS THE SAME AND YOU WANT MORE CONFIDENCE OF COVERING THE TRUE POPULATION VALUE, YOU NEED A LARGER MARGIN OF ERROR, WHICH RESULTS IN A WIDER CONFIDENCE INTERVAL.
This verified answer contains over 370 words.
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