andrew_gelman_stats andrew_gelman_stats-2012 andrew_gelman_stats-2012-1362 knowledge-graph by maker-knowledge-mining
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Introduction: 24. A supermarket chain has 100 equally-sized stores. It is desired to estimate the proportion of vegetables that spoil before being sold. The following sampling designs are considered: (a) Sample 10 stores, then sample half the vegetables within each of these stores; or (b) Sample 20 stores, then sample one-quarter of the vegetables within each of these stores. Which of these designs has the lowest variance? Why might the higher-variance design still be chosen? Solution to question 23 From yesterday : 23. Suppose you are conducting a survey in which people are asked about their health behaviors (how often they wash their hands, how often they go to the doctor, etc.). There is a concern that different interviewers will get different sorts of responses—that is, there may be important interviewer effects. Describe (in two sentences) how you could estimate the interviewer effects within your survey. Can the interviewer effects create problems of reliability of the survey r
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1 It is desired to estimate the proportion of vegetables that spoil before being sold. [sent-3, score-0.584]
2 The following sampling designs are considered: (a) Sample 10 stores, then sample half the vegetables within each of these stores; or (b) Sample 20 stores, then sample one-quarter of the vegetables within each of these stores. [sent-4, score-1.348]
3 Which of these designs has the lowest variance? [sent-5, score-0.226]
4 Solution to question 23 From yesterday : 23. [sent-7, score-0.056]
5 Suppose you are conducting a survey in which people are asked about their health behaviors (how often they wash their hands, how often they go to the doctor, etc. [sent-8, score-0.603]
6 There is a concern that different interviewers will get different sorts of responses—that is, there may be important interviewer effects. [sent-10, score-1.155]
7 Describe (in two sentences) how you could estimate the interviewer effects within your survey. [sent-11, score-0.873]
8 Can the interviewer effects create problems of reliability of the survey responses? [sent-12, score-1.262]
9 Can the interviewer effects create problems of validity of the survey responses? [sent-14, score-1.235]
10 Solution: You can do a survey experiment and randomly assign different respondents to different interviewers. [sent-16, score-0.734]
11 ) of responses for each interviewer, and compare (ideally using a graph! [sent-19, score-0.362]
12 Yes, interviewer effects can create problems of reliability (different interviewers getting different results) and validity (responses being different from the truth). [sent-21, score-1.746]
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same-blog 1 0.99999982 1362 andrew gelman stats-2012-06-03-Question 24 of my final exam for Design and Analysis of Sample Surveys
Introduction: 24. A supermarket chain has 100 equally-sized stores. It is desired to estimate the proportion of vegetables that spoil before being sold. The following sampling designs are considered: (a) Sample 10 stores, then sample half the vegetables within each of these stores; or (b) Sample 20 stores, then sample one-quarter of the vegetables within each of these stores. Which of these designs has the lowest variance? Why might the higher-variance design still be chosen? Solution to question 23 From yesterday : 23. Suppose you are conducting a survey in which people are asked about their health behaviors (how often they wash their hands, how often they go to the doctor, etc.). There is a concern that different interviewers will get different sorts of responses—that is, there may be important interviewer effects. Describe (in two sentences) how you could estimate the interviewer effects within your survey. Can the interviewer effects create problems of reliability of the survey r
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Introduction: 23. Suppose you are conducting a survey in which people are asked about their health behaviors (how often they wash their hands, how often they go to the doctor, etc.). There is a concern that different interviewers will get different sorts of responses—that is, there may be important interviewer effects. Describe (in two sentences) how you could estimate the interviewer effects within your survey. Can the interviewer effects create problems of reliability of the survey responses? Explain (in one sentence). Can the interviewer effects create problems of validity of the survey responses? Explain (in one sentence). Solution to question 22 From yesterday : 22. A supermarket chain has 100 equally-sized stores. It is desired to estimate the proportion of vegetables that spoil before being sold. Three stores are selected at random and are checked: the percent of spoiled vegetables are 3%, 5%, and 10% in the three stores. Give an estimate and standard error for the percentage of spo
3 0.3778393 1365 andrew gelman stats-2012-06-04-Question 25 of my final exam for Design and Analysis of Sample Surveys
Introduction: 25. You are using multilevel regression and poststratification (MRP) to a survey of 1500 people to estimate support for the space program, by state. The model is fit using, as a state- level predictor, the Republican presidential vote in the state, which turns out to have a low correlation with support for the space program. Which of the following statements are basically true? (Indicate all that apply.) (a) For small states, the MRP estimates will be determined almost entirely by the demo- graphic characteristics of the respondents in the sample from that state. (b) For small states, the MRP estimates will be determined almost entirely by the demographic characteristics of the population in that state. (c) Adding a predictor specifically for this model (for example, a measure of per-capita space-program spending in the state) could dramatically improve the estimates of state-level opinion. (d) It would not be appropriate to add a predictor such as per-capita space-program spen
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Introduction: 22. A supermarket chain has 100 equally-sized stores. It is desired to estimate the proportion of vegetables that spoil before being sold. Three stores are selected at random and are checked: the percent of spoiled vegetables are 3%, 5%, and 10% in the three stores. Give an estimate and standard error for the percentage of spoiled vegetables for the entire chain. Solution to question 21 From yesterday : 21. A country is divided into three regions with populations of 2 million, 2 million, and 0.5 million, respectively. A survey is done asking about foreign policy opinions. Somebody proposes taking a sample of 50 people from each reason. Give a reason why this non-proportional sample would not usually be done, and also a reason why it might actually be a good idea. Solution: Nonproportional sampling is usually avoided because it makes the analysis more complicated and it results in a higher standard error for estimates of the general population. It might be a good idea her
5 0.15569469 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
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Introduction: 24. A supermarket chain has 100 equally-sized stores. It is desired to estimate the proportion of vegetables that spoil before being sold. The following sampling designs are considered: (a) Sample 10 stores, then sample half the vegetables within each of these stores; or (b) Sample 20 stores, then sample one-quarter of the vegetables within each of these stores. Which of these designs has the lowest variance? Why might the higher-variance design still be chosen? Solution to question 23 From yesterday : 23. Suppose you are conducting a survey in which people are asked about their health behaviors (how often they wash their hands, how often they go to the doctor, etc.). There is a concern that different interviewers will get different sorts of responses—that is, there may be important interviewer effects. Describe (in two sentences) how you could estimate the interviewer effects within your survey. Can the interviewer effects create problems of reliability of the survey r
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Introduction: 23. Suppose you are conducting a survey in which people are asked about their health behaviors (how often they wash their hands, how often they go to the doctor, etc.). There is a concern that different interviewers will get different sorts of responses—that is, there may be important interviewer effects. Describe (in two sentences) how you could estimate the interviewer effects within your survey. Can the interviewer effects create problems of reliability of the survey responses? Explain (in one sentence). Can the interviewer effects create problems of validity of the survey responses? Explain (in one sentence). Solution to question 22 From yesterday : 22. A supermarket chain has 100 equally-sized stores. It is desired to estimate the proportion of vegetables that spoil before being sold. Three stores are selected at random and are checked: the percent of spoiled vegetables are 3%, 5%, and 10% in the three stores. Give an estimate and standard error for the percentage of spo
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Introduction: 22. A supermarket chain has 100 equally-sized stores. It is desired to estimate the proportion of vegetables that spoil before being sold. Three stores are selected at random and are checked: the percent of spoiled vegetables are 3%, 5%, and 10% in the three stores. Give an estimate and standard error for the percentage of spoiled vegetables for the entire chain. Solution to question 21 From yesterday : 21. A country is divided into three regions with populations of 2 million, 2 million, and 0.5 million, respectively. A survey is done asking about foreign policy opinions. Somebody proposes taking a sample of 50 people from each reason. Give a reason why this non-proportional sample would not usually be done, and also a reason why it might actually be a good idea. Solution: Nonproportional sampling is usually avoided because it makes the analysis more complicated and it results in a higher standard error for estimates of the general population. It might be a good idea her
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Introduction: 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 estimates of time trends in religious attendance? Solution to question 3 From yesterday : 3. We discussed in class the best currently available method for estimating the proportion of military servicemembers who are gay. What is that method? (Recall the problems with the direct approach: there is no simple way to survey servicemembers at random, nor is it likely that they would answer such a question honestly.) Solution: I was talking about the work of Gary Gates, combining an estimate of the percentage of gays in the population with an estimate of the probability that someone is in the military, given that he or she is gay.
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Introduction: 17. In a survey of n people, half are asked if they support “the health care law recently passed by Congress” and half are asked if they support “the law known as Obamacare.” The goal is to estimate the effect of the wording on the proportion of Yes responses. How large must n be for the effect to be estimated within a standard error of 5 percentage points? Solution to question 16 From yesterday : 16. You are doing a survey in a war-torn country to estimate what percentage of unemployed men support the rebels in a civil war. Express this as a ratio estimation problem, where goal is to estimate Y.bar/X.bar. What are x and y here? Give the estimate and standard error for the percentage of unemployed men who support the rebels. Solution: x is 1 if the respondent is an unemployed man, 0 otherwise. y is 1 if the respondent is an unemployed man and supports the rebels, 0 otherwise. The estimate is y.bar/x.bar [typo fixed], the standard error is (1/x.bar)*(1/sqrt(n))*s.z, whe
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Introduction: 24. A supermarket chain has 100 equally-sized stores. It is desired to estimate the proportion of vegetables that spoil before being sold. The following sampling designs are considered: (a) Sample 10 stores, then sample half the vegetables within each of these stores; or (b) Sample 20 stores, then sample one-quarter of the vegetables within each of these stores. Which of these designs has the lowest variance? Why might the higher-variance design still be chosen? Solution to question 23 From yesterday : 23. Suppose you are conducting a survey in which people are asked about their health behaviors (how often they wash their hands, how often they go to the doctor, etc.). There is a concern that different interviewers will get different sorts of responses—that is, there may be important interviewer effects. Describe (in two sentences) how you could estimate the interviewer effects within your survey. Can the interviewer effects create problems of reliability of the survey r
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Introduction: 23. Suppose you are conducting a survey in which people are asked about their health behaviors (how often they wash their hands, how often they go to the doctor, etc.). There is a concern that different interviewers will get different sorts of responses—that is, there may be important interviewer effects. Describe (in two sentences) how you could estimate the interviewer effects within your survey. Can the interviewer effects create problems of reliability of the survey responses? Explain (in one sentence). Can the interviewer effects create problems of validity of the survey responses? Explain (in one sentence). Solution to question 22 From yesterday : 22. A supermarket chain has 100 equally-sized stores. It is desired to estimate the proportion of vegetables that spoil before being sold. Three stores are selected at random and are checked: the percent of spoiled vegetables are 3%, 5%, and 10% in the three stores. Give an estimate and standard error for the percentage of spo
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