StatTutor Lesson - Large-Sample Confidence Intervals for Comparing Proportions

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Large-sample confidence interval for comparing proportions
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      Question 1

      62

      Question 1.

      What is the name for the point estimate: p^1 - p^2?

      A.
      B.
      C.
      D.

      Incorrect. The name for p^1 - p^2 is the difference between two sample proportions. This is a statistic.
      Correct. The name for p^1 - p^2 is the difference between two sample proportions. This is a statistic.
      Incorrect. Try again.
      2

      Question 2

      120

      Question 2.

      What is the name of the parameter we wish to estimate with a confidence interval for p1 - p2?

      A.
      B.
      C.
      D.

      Incorrect. The name for p1 - p2 is the difference between two population proportions.
      Correct. The name for p1 - p2 is the difference between two population proportions.
      Incorrect. Try again.
      2

      Question 3

      152

      Question 3.

      What is the problem with the formula: p^1p^2±zp1(1p1)n1+p2(1p2)n2?

      A.
      B.
      C.

      Incorrect. The values for p1 and p2 are unknown as we are trying to estimate them and yet the formula requires values for them.
      Correct. The values for p1 and p2 are unknown as we are trying to estimate them and yet the formula requires values for them.
      Incorrect. Try again.
      2

      Question 4

      195

      Question 4.

      In addition to appropriately collected data, what condition is necessary for using the formula: p^1p^2±zp1(1p1)n1+p2(1p2)n2?

      A.
      B.
      C.

      Incorrect. n1p^15, n1(1p^1)5, n2p^25, and n2(1p^2)5 is the other necessary condition. These are actually the observed counts in all four cells—they all need to be five or bigger.
      Correct. n1p^15, n1(1p^1)5, n2p^25, and n2(1p^2)5 is the other necessary condition. These are actually the observed counts in all four cells—they all need to be five or bigger.
      Incorrect. Try again.
      2

      Question 5

      268

      Question 5.

      In order to estimate p1 - p2 with a confidence interval, which is NOT an appropriate method of data collection?

      A.
      B.
      C.

      Incorrect. Matched pairs data should never be analyzed with this two-sample procedure for estimating p1 - p2 with a confidence interval.
      Correct. Matched pairs data should never be analyzed with this two-sample procedure for estimating p1 - p2 with a confidence interval.
      Incorrect. Try again.
      2

      Question 6

      294

      Question 6.

      What is the name for: zp^1(1p^1)n1+p^2(1p^2)n2?

      A.
      B.

      Correct. The name for zp^1(1p^1)n1+p^2(1p^2)n2 is margin of error.
      Incorrect. Try again.
      2
      Incorrect. The name forzp^1(1p^1)n1+p^2(1p^2)n2 is margin of error.

      Questions 7-8

      346

      Question 7.

      For this example, were the data appropriately collected with either two separate simple random samples or with random allocation in an experiment?

      A.
      B.

      Incorrect. Data were collected using a randomized experiment with subjects randomly allocated to treatments.
      Correct. Data were collected using a randomized experiment with subjects randomly allocated to treatments.
      Incorrect. Try again.
      2

      Question 9

      463

      Question 9.

      What is the value of z* for 95% confidence?

      A.
      B.
      C.
      D.

      Incorrect. The value of z* for 95% confidence is 1.960.
      Correct. The value of z* for 95% confidence is 1.960.
      Incorrect. Try again.
      2

      Question 10

      527

      Question 10.

      What is the name for the value 0.003?

      A.
      B.

      Incorrect. The name for the value 0.003 is margin of error.
      Correct. The name for the value 0.003 is margin of error.
      Incorrect. Try again.
      2

      Question 11

      541

      Question 11.

      What is another way to correctly interpret this confidence interval?

      A.
      B.

      Incorrect. This confidence interval estimates p1 - p2 or the difference between the two treatment proportions. p1= proportion of doctors having a heart attack while taking aspiring and p2 = the proportion of doctors having a heart attack while taking a placebo. Thus, the interval tells us that the difference between the proportion of doctors taking aspirin having a heart attack and the proportion of doctors taking a placbo having a heart attack is somewhere -0.011 and -0.005 with 95% confidence.
      Correct. This confidence interval estimates p1 - p2 or the difference between the two treatment proportions. p1= proportion of doctors having a heart attack while taking aspiring and p2 = the proportion of doctors having a heart attack while taking a placebo. Thus, the interval tells us that the difference between the proportion of doctors taking aspirin having a heart attack and the proportion of doctors taking a placbo having a heart attack is somewhere -0.011 and -0.005 with 95% confidence.
      Incorrect. Try again.
      2

      Question 12

      588

      Question 12.

      Do you think the results for all adults in the general public will be the same as or different from doctors?

      A.
      B.

      Incorrect. The answer to this question is subject to debate. Depending on how you look at it both answers could be correct. Some say that doctors don't take very good care of their physical health. Others might argue that doctors are more aware of potential outcomes. What is your opinion?
      Correct. The answer to this question is subject to debate. Depending on how you look at it both answers could be correct. Some say that doctors don't take very good care of their physical health. Others might argue that doctors are more aware of potential outcomes. What is your opinion?
      Incorrect. Try again.
      2