andrew_gelman_stats andrew_gelman_stats-2012 andrew_gelman_stats-2012-1368 knowledge-graph by maker-knowledge-mining
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Introduction: 27. Which of the following problems were identified with the Burnham et al. survey of Iraq mortality? (Indicate all that apply.) (a) The survey used cluster sampling, which is inappropriate for estimating individual out- comes such as death. (b) In their report, Burnham et al. did not identify their primary sampling units. (c) The second-stage sampling was not a probability sample. (d) Survey materials supplied by the authors are incomplete and inconsistent with published descriptions of the survey. Solution to question 26 From yesterday : 26. You have just graded an an exam with 28 questions and 15 students. You fit a logistic item- response model estimating ability, difficulty, and discrimination parameters. Which of the following statements are basically true? (Indicate all that apply.) (a) If a question is answered correctly by students with very low and very high ability, but is missed by students in the middle, it will have a high value for its discrimination
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1 Which of the following problems were identified with the Burnham et al. [sent-2, score-0.346]
2 ) (a) The survey used cluster sampling, which is inappropriate for estimating individual out- comes such as death. [sent-5, score-0.46]
3 (c) The second-stage sampling was not a probability sample. [sent-8, score-0.183]
4 (d) Survey materials supplied by the authors are incomplete and inconsistent with published descriptions of the survey. [sent-9, score-0.512]
5 Solution to question 26 From yesterday : 26. [sent-10, score-0.201]
6 You have just graded an an exam with 28 questions and 15 students. [sent-11, score-0.506]
7 You fit a logistic item- response model estimating ability, difficulty, and discrimination parameters. [sent-12, score-0.771]
8 ) (a) If a question is answered correctly by students with very low and very high ability, but is missed by students in the middle, it will have a high value for its discrimination parameter. [sent-15, score-1.415]
9 (b) It is not possible to fit an item-response model when you have more questions than students. [sent-16, score-0.559]
10 In order to fit the model, you either need to reduce the number of questions (for example, by discarding some questions or by putting together some questions into a combined score) or increase the number of students in the dataset. [sent-17, score-1.763]
11 (c) To keep the model identified, you can set one of the difficulty parameters or one of the ability parameters to zero and set one of the discrimination parameters to 1. [sent-18, score-1.634]
12 (d) If two students answer the same number of questions correctly, they will have the same estimated ability parameter. [sent-19, score-0.922]
13 (e) Under the model, if a student’s ability parameter has the same value as a particular question’s difficulty parameter, there is a 50% chance the student will get the question right. [sent-20, score-1.003]
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same-blog 1 1.0000001 1368 andrew gelman stats-2012-06-06-Question 27 of my final exam for Design and Analysis of Sample Surveys
Introduction: 27. Which of the following problems were identified with the Burnham et al. survey of Iraq mortality? (Indicate all that apply.) (a) The survey used cluster sampling, which is inappropriate for estimating individual out- comes such as death. (b) In their report, Burnham et al. did not identify their primary sampling units. (c) The second-stage sampling was not a probability sample. (d) Survey materials supplied by the authors are incomplete and inconsistent with published descriptions of the survey. Solution to question 26 From yesterday : 26. You have just graded an an exam with 28 questions and 15 students. You fit a logistic item- response model estimating ability, difficulty, and discrimination parameters. Which of the following statements are basically true? (Indicate all that apply.) (a) If a question is answered correctly by students with very low and very high ability, but is missed by students in the middle, it will have a high value for its discrimination
2 0.64367521 1367 andrew gelman stats-2012-06-05-Question 26 of my final exam for Design and Analysis of Sample Surveys
Introduction: 26. You have just graded an an exam with 28 questions and 15 students. You fit a logistic item- response model estimating ability, difficulty, and discrimination parameters. Which of the following statements are basically true? (Indicate all that apply.) (a) If a question is answered correctly by students with very low and very high ability, but is missed by students in the middle, it will have a high value for its discrimination parameter. (b) It is not possible to fit an item-response model when you have more questions than students. In order to fit the model, you either need to reduce the number of questions (for example, by discarding some questions or by putting together some questions into a combined score) or increase the number of students in the dataset. (c) To keep the model identified, you can set one of the difficulty parameters or one of the ability parameters to zero and set one of the discrimination parameters to 1. (d) If two students answer the same number of q
3 0.38783228 1371 andrew gelman stats-2012-06-07-Question 28 of my final exam for Design and Analysis of Sample Surveys
Introduction: This is it, the last question on the exam! 28. A telephone survey was conducted several years ago, asking people how often they were polled in the past year. I can’t recall the responses, but suppose that 40% of the respondents said they participated in zero surveys in the previous year, 30% said they participated in one survey, 15% said two surveys, 10% said three, and 5% said four. From this it is easy to estimate an average, but there is a worry that this survey will itself overrepresent survey participants and thus overestimate the rate at which the average person is surveyed. Come up with a procedure to use these data to get an improved estimate of the average number of surveys that a randomly-sampled American is polled in a year. Solution to question 27 From yesterday : 27. Which of the following problems were identified with the Burnham et al. survey of Iraq mortality? (Indicate all that apply.) (a) The survey used cluster sampling, which is inappropriate for estim
4 0.1938352 5 andrew gelman stats-2010-04-27-Ethical and data-integrity problems in a study of mortality in Iraq
Introduction: Michael Spagat notifies me that his article criticizing the 2006 study of Burnham, Lafta, Doocy and Roberts has just been published . The Burnham et al. paper (also called, to my irritation (see the last item here ), “the Lancet survey”) used a cluster sample to estimate the number of deaths in Iraq in the three years following the 2003 invasion. In his newly-published paper, Spagat writes: [The Spagat article] presents some evidence suggesting ethical violations to the survey’s respondents including endangerment, privacy breaches and violations in obtaining informed consent. Breaches of minimal disclosure standards examined include non-disclosure of the survey’s questionnaire, data-entry form, data matching anonymised interviewer identifications with households and sample design. The paper also presents some evidence relating to data fabrication and falsification, which falls into nine broad categories. This evidence suggests that this survey cannot be considered a reliable or
Introduction: In response to my remarks on his online book, Think Bayes, Allen Downey wrote: I [Downey] have a question about one of your comments: My [Gelman's] main criticism with both books is that they talk a lot about inference but not so much about model building or model checking (recall the three steps of Bayesian data analysis). I think it’s ok for an introductory book to focus on inference, which of course is central to the data-analytic process—but I’d like them to at least mention that Bayesian ideas arise in model building and model checking as well. This sounds like something I agree with, and one of the things I tried to do in the book is to put modeling decisions front and center. But the word “modeling” is used in lots of ways, so I want to see if we are talking about the same thing. For example, in many chapters, I start with a simple model of the scenario, do some analysis, then check whether the model is good enough, and iterate. Here’s the discussion of modeling
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Introduction: 27. Which of the following problems were identified with the Burnham et al. survey of Iraq mortality? (Indicate all that apply.) (a) The survey used cluster sampling, which is inappropriate for estimating individual out- comes such as death. (b) In their report, Burnham et al. did not identify their primary sampling units. (c) The second-stage sampling was not a probability sample. (d) Survey materials supplied by the authors are incomplete and inconsistent with published descriptions of the survey. Solution to question 26 From yesterday : 26. You have just graded an an exam with 28 questions and 15 students. You fit a logistic item- response model estimating ability, difficulty, and discrimination parameters. Which of the following statements are basically true? (Indicate all that apply.) (a) If a question is answered correctly by students with very low and very high ability, but is missed by students in the middle, it will have a high value for its discrimination
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Introduction: 26. You have just graded an an exam with 28 questions and 15 students. You fit a logistic item- response model estimating ability, difficulty, and discrimination parameters. Which of the following statements are basically true? (Indicate all that apply.) (a) If a question is answered correctly by students with very low and very high ability, but is missed by students in the middle, it will have a high value for its discrimination parameter. (b) It is not possible to fit an item-response model when you have more questions than students. In order to fit the model, you either need to reduce the number of questions (for example, by discarding some questions or by putting together some questions into a combined score) or increase the number of students in the dataset. (c) To keep the model identified, you can set one of the difficulty parameters or one of the ability parameters to zero and set one of the discrimination parameters to 1. (d) If two students answer the same number of q
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Introduction: 6. A survey of New York City residents is performed using cluster sampling. The design effect is 3.0. From the survey, the estimated proportion who prefer the Mets to the Yankees is 0.42 with a standard error of 0.05. How many people were in the sample? Solution to question 5 From yesterday : 5. Which of the following better describes changes in public opinion on most issues? (Choose only one.) (a) Dynamic stability: On any given issue, average opinion remains stable but liberals and conservatives move back and forth in opposite directions (the “accordion model”) (b) Uniform swing: Average opinion on an issue can move but the liberals and conservatives don’t move much relative to each other (the disribution of opinions is a “solid block of wood”) (c) Compensating tradeoffs: When considering multiple survey questions on the same general topic, average opinion can move sharply to the left or right on individual questions while the average over all the questions remains st
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Introduction: 5. Which of the following better describes changes in public opinion on most issues? (Choose only one.) (a) Dynamic stability: On any given issue, average opinion remains stable but liberals and conservatives move back and forth in opposite directions (the “accordion model”) (b) Uniform swing: Average opinion on an issue can move but the liberals and conservatives don’t move much relative to each other (the disribution of opinions is a “solid block of wood”) (c) Compensating tradeoffs: When considering multiple survey questions on the same general topic, average opinion can move sharply to the left or right on individual questions while the average over all the questions remains stable (the “rubber band model”) Solution to question 4 From yesterday : 4. Researchers have found that survey respondents overreport church attendance. Thus, naive estimates from surveys overstate the percentage of Americans who attend church regularly. Does this have a large impact on estimate
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Introduction: This is it, the last question on the exam! 28. A telephone survey was conducted several years ago, asking people how often they were polled in the past year. I can’t recall the responses, but suppose that 40% of the respondents said they participated in zero surveys in the previous year, 30% said they participated in one survey, 15% said two surveys, 10% said three, and 5% said four. From this it is easy to estimate an average, but there is a worry that this survey will itself overrepresent survey participants and thus overestimate the rate at which the average person is surveyed. Come up with a procedure to use these data to get an improved estimate of the average number of surveys that a randomly-sampled American is polled in a year. Solution to question 27 From yesterday : 27. Which of the following problems were identified with the Burnham et al. survey of Iraq mortality? (Indicate all that apply.) (a) The survey used cluster sampling, which is inappropriate for estim
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Introduction: 27. Which of the following problems were identified with the Burnham et al. survey of Iraq mortality? (Indicate all that apply.) (a) The survey used cluster sampling, which is inappropriate for estimating individual out- comes such as death. (b) In their report, Burnham et al. did not identify their primary sampling units. (c) The second-stage sampling was not a probability sample. (d) Survey materials supplied by the authors are incomplete and inconsistent with published descriptions of the survey. Solution to question 26 From yesterday : 26. You have just graded an an exam with 28 questions and 15 students. You fit a logistic item- response model estimating ability, difficulty, and discrimination parameters. Which of the following statements are basically true? (Indicate all that apply.) (a) If a question is answered correctly by students with very low and very high ability, but is missed by students in the middle, it will have a high value for its discrimination
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