andrew_gelman_stats andrew_gelman_stats-2012 andrew_gelman_stats-2012-1341 knowledge-graph by maker-knowledge-mining
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Introduction: 14. A public health survey of elderly Americans includes many questions, including “How many hours per week did you exercise in your most active years as a young adult?” and also several questions about current mobility and health status. Response rates are high for the questions about recent activities and status, but there is a lot of nonresponse for the question on past activity. You are considering imputing the missing values on the question, “How many hours per week did you exercise in your most active years as a young adult?” Which of the following statements are basically correct? (Indicate all that apply.) (a) If done reasonably well, imputation is preferred to available-case and complete-case analysis. (b) If you do impute, you should also present the available-case and complete-case analysis and analyze how the imputed estimates differ. (c) It is OK to include current health status variables as predictors in a model imputing past activities: anything that adds informati
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1 A public health survey of elderly Americans includes many questions, including “How many hours per week did you exercise in your most active years as a young adult? [sent-2, score-1.457]
2 ” and also several questions about current mobility and health status. [sent-3, score-0.592]
3 Response rates are high for the questions about recent activities and status, but there is a lot of nonresponse for the question on past activity. [sent-4, score-0.781]
4 You are considering imputing the missing values on the question, “How many hours per week did you exercise in your most active years as a young adult? [sent-5, score-1.095]
5 ) (a) If done reasonably well, imputation is preferred to available-case and complete-case analysis. [sent-8, score-0.138]
6 (b) If you do impute, you should also present the available-case and complete-case analysis and analyze how the imputed estimates differ. [sent-9, score-0.157]
7 (c) It is OK to include current health status variables as predictors in a model imputing past activities: anything that adds information is good when imputing. [sent-10, score-1.321]
8 (d) It is probably not a good idea to include current health status variables as predictors in a model imputing past activities: current health is possibly influenced by past activities, and including a casual outcome can bias estimates of a treatment variable. [sent-11, score-2.156]
9 (e) If you fit a regression model and impute your best prediction for each person (rather than imputing random draws from the predictive distribution), you can have problems because you will be more likely to impute extreme values. [sent-12, score-1.022]
10 (f) It is a good idea to fit a logistic regression predicting response/nonresponse to the question of interest as a way to look for systematic differences between respondents and nonrespondents on this question. [sent-13, score-0.407]
11 Solution to question 13 From yesterday : 13. [sent-14, score-0.156]
12 A survey of American adults is conducted that includes too many women and not enough men in the sample. [sent-15, score-0.793]
13 In the resulting weighting, each female respondent is given a weight of 1 and each male respondent is given a weight of 1. [sent-16, score-0.733]
14 The sample includes 600 women and 380 men, of whom 400 women and 100 men respond Yes to a particular question of interest. [sent-18, score-0.808]
15 Give an estimate and standard error for the proportion of American adults who would answer Yes to this question if asked. [sent-19, score-0.514]
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Introduction: 14. A public health survey of elderly Americans includes many questions, including “How many hours per week did you exercise in your most active years as a young adult?” and also several questions about current mobility and health status. Response rates are high for the questions about recent activities and status, but there is a lot of nonresponse for the question on past activity. You are considering imputing the missing values on the question, “How many hours per week did you exercise in your most active years as a young adult?” Which of the following statements are basically correct? (Indicate all that apply.) (a) If done reasonably well, imputation is preferred to available-case and complete-case analysis. (b) If you do impute, you should also present the available-case and complete-case analysis and analyze how the imputed estimates differ. (c) It is OK to include current health status variables as predictors in a model imputing past activities: anything that adds informati
2 0.79273611 1344 andrew gelman stats-2012-05-25-Question 15 of my final exam for Design and Analysis of Sample Surveys
Introduction: 15. A researcher conducts a random-digit-dial survey of individuals and married couples. The design is as follows: if only one person lives in a household, he or she is interviewed. If there are multiple adults in the household, one is selected at random: he or she is interviewed and, if he or she is married to one of the other adults in the household, the spouse is interviewed as well. Come up with a scheme for inverse-probability weights (ignoring nonresponse and assuming there is exactly one phone line per household). Solution to question 14 From yesterday : 14. A public health survey of elderly Americans includes many questions, including “How many hours per week did you exercise in your most active years as a young adult?” and also several questions about current mobility and health status. Response rates are high for the questions about recent activities and status, but there is a lot of nonresponse for the question on past activity. You are considering imputing the mis
3 0.29397932 1340 andrew gelman stats-2012-05-23-Question 13 of my final exam for Design and Analysis of Sample Surveys
Introduction: 13. A survey of American adults is conducted that includes too many women and not enough men in the sample. In the resulting weighting, each female respondent is given a weight of 1 and each male respondent is given a weight of 1.5. The sample includes 600 women and 380 men, of whom 400 women and 100 men respond Yes to a particular question of interest. Give an estimate and standard error for the proportion of American adults who would answer Yes to this question if asked. Solution to question 12 From yesterday : 12. A researcher fits a regression model predicting some political behavior given predictors for demographics and several measures of economic ideology. The coefficients for the ideology measures are not statistically significant, and the researcher creates a new measure, adding up the ideology questions and creating a common score, and then fits a new regression including the new score and removing the individual ideology questions from the model. Which of the follo
4 0.19235271 935 andrew gelman stats-2011-10-01-When should you worry about imputed data?
Introduction: Majid Ezzati writes: My research group is increasingly focusing on a series of problems that involve data that either have missingness or measurements that may have bias/error. We have at times developed our own approaches to imputation (as simple as interpolating a missing unit and as sophisticated as a problem-specific Bayesian hierarchical model) and at other times, other groups impute the data. The outputs are being used to investigate the basic associations between pairs of variables, Xs and Ys, in regressions; we may or may not interpret these as causal. I am contacting colleagues with relevant expertise to suggest good references on whether having imputed X and/or Y in a subsequent regression is correct or if it could somehow lead to biased/spurious associations. Thinking about this, we can have at least the following situations (these could all be Bayesian or not): 1) X and Y both measured (perhaps with error) 2) Y imputed using some data and a model and X measur
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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: 14. A public health survey of elderly Americans includes many questions, including “How many hours per week did you exercise in your most active years as a young adult?” and also several questions about current mobility and health status. Response rates are high for the questions about recent activities and status, but there is a lot of nonresponse for the question on past activity. You are considering imputing the missing values on the question, “How many hours per week did you exercise in your most active years as a young adult?” Which of the following statements are basically correct? (Indicate all that apply.) (a) If done reasonably well, imputation is preferred to available-case and complete-case analysis. (b) If you do impute, you should also present the available-case and complete-case analysis and analyze how the imputed estimates differ. (c) It is OK to include current health status variables as predictors in a model imputing past activities: anything that adds informati
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Introduction: 15. A researcher conducts a random-digit-dial survey of individuals and married couples. The design is as follows: if only one person lives in a household, he or she is interviewed. If there are multiple adults in the household, one is selected at random: he or she is interviewed and, if he or she is married to one of the other adults in the household, the spouse is interviewed as well. Come up with a scheme for inverse-probability weights (ignoring nonresponse and assuming there is exactly one phone line per household). Solution to question 14 From yesterday : 14. A public health survey of elderly Americans includes many questions, including “How many hours per week did you exercise in your most active years as a young adult?” and also several questions about current mobility and health status. Response rates are high for the questions about recent activities and status, but there is a lot of nonresponse for the question on past activity. You are considering imputing the mis
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Introduction: 13. A survey of American adults is conducted that includes too many women and not enough men in the sample. In the resulting weighting, each female respondent is given a weight of 1 and each male respondent is given a weight of 1.5. The sample includes 600 women and 380 men, of whom 400 women and 100 men respond Yes to a particular question of interest. Give an estimate and standard error for the proportion of American adults who would answer Yes to this question if asked. Solution to question 12 From yesterday : 12. A researcher fits a regression model predicting some political behavior given predictors for demographics and several measures of economic ideology. The coefficients for the ideology measures are not statistically significant, and the researcher creates a new measure, adding up the ideology questions and creating a common score, and then fits a new regression including the new score and removing the individual ideology questions from the model. Which of the follo
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Introduction: 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 to question 15 From yesterday : 15. A researcher conducts a random-digit-dial survey of individuals and married couples. The design is as follows: if only one person lives in a household, he or she is interviewed. If there are multiple adults in the household, one is selected at random: he or she is interviewed and, if he or she is married to one of the other adults in the household, the spouse is interviewed as well. Come up with a scheme for inverse-probability weights (ignoring nonresponse and assuming there is exactly one phone line per household). Solution: Your probability of being selected is proportional to: (1/(#adults in yo
5 0.67827314 784 andrew gelman stats-2011-07-01-Weighting and prediction in sample surveys
Introduction: A couple years ago Rod Little was invited to write an article for the diamond jubilee of the Calcutta Statistical Association Bulletin. His article was published with discussions from Danny Pfefferman, J. N. K. Rao, Don Rubin, and myself. Here it all is . I’ll paste my discussion below, but it’s worth reading the others’ perspectives too. Especially the part in Rod’s rejoinder where he points out a mistake I made. Survey weights, like sausage and legislation, are designed and best appreciated by those who are placed a respectable distance from their manufacture. For those of us working inside the factory, vigorous discussion of methods is appreciated. I enjoyed Rod Little’s review of the connections between modeling and survey weighting and have just a few comments. I like Little’s discussion of model-based shrinkage of post-stratum averages, which, as he notes, can be seen to correspond to shrinkage of weights. I would only add one thing to his formula at the end of his
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Introduction: 15. A researcher conducts a random-digit-dial survey of individuals and married couples. The design is as follows: if only one person lives in a household, he or she is interviewed. If there are multiple adults in the household, one is selected at random: he or she is interviewed and, if he or she is married to one of the other adults in the household, the spouse is interviewed as well. Come up with a scheme for inverse-probability weights (ignoring nonresponse and assuming there is exactly one phone line per household). Solution to question 14 From yesterday : 14. A public health survey of elderly Americans includes many questions, including “How many hours per week did you exercise in your most active years as a young adult?” and also several questions about current mobility and health status. Response rates are high for the questions about recent activities and status, but there is a lot of nonresponse for the question on past activity. You are considering imputing the mis
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Introduction: 14. A public health survey of elderly Americans includes many questions, including “How many hours per week did you exercise in your most active years as a young adult?” and also several questions about current mobility and health status. Response rates are high for the questions about recent activities and status, but there is a lot of nonresponse for the question on past activity. You are considering imputing the missing values on the question, “How many hours per week did you exercise in your most active years as a young adult?” Which of the following statements are basically correct? (Indicate all that apply.) (a) If done reasonably well, imputation is preferred to available-case and complete-case analysis. (b) If you do impute, you should also present the available-case and complete-case analysis and analyze how the imputed estimates differ. (c) It is OK to include current health status variables as predictors in a model imputing past activities: anything that adds informati
3 0.97988129 1539 andrew gelman stats-2012-10-18-IRB nightmares
Introduction: Andrew Perrin nails it : Twice a year, like clockwork, the ethics cops at the IRB [institutional review board, the group on campus that has to approve research involving human subjects] take a break from deciding whether or not radioactive isotopes can be administered to prison populations to cure restless-leg syndrome to dream up some fancy new way in which participating in an automated telephone poll might cause harm. Perrin adds: The list of exemptions to IRB review is too short and, more importantly, contains no guiding principle as to what makes exempt. . . . [and] Even exemptions require approval by the IRB. He also voices a thought I’ve had many times, which is that there are all sorts of things you or I or anyone else can do on the street (for example, go up to people and ask them personal questions, drop objects and see if people pick them up, stage fights with our friends to see the reactions of bystanders, etc etc etc) but for which we have to go through an IRB
Introduction: Amanda Martinez, a writer for The Atlantic and others, advised attendees that her favorite writing “accorded me the basic human dignity of allowing me to draw my own conclusions.” I really like that way of putting it, and this is something we tried hard to do with Red State Blue State, to put the information and our reasoning right there in front of the reader, rather than hiding behind a bunch of statistically-significant regression coefficients. This is related to the idea of presenting research findings quantitatively (which, I think, lends itself to clearer statements of uncertainty and variation) rather than qualitatively (which seems to come out more deterministically, as “X causes Y” or “when A happens, B happens”). The above quote comes from a conference of students organized by Nathan Sanders, who writes: Thanks so much for posting an announcement about the Communicating Science workshop (ComSciCon) back in January! With the help of your blog, we received more than
Introduction: I read this front-page New York Times article and was immediately suspicious. Here’s the story (from reporter Gina Kolata): Could exercise actually be bad for some healthy people? A well-known group of researchers, including one who helped write the scientific paper justifying national guidelines that promote exercise for all, say the answer may be a qualified yes. By analyzing data from six rigorous exercise studies involving 1,687 people, the group found that about 10 percent actually got worse on at least one of the measures related to heart disease: blood pressure and levels of insulin, HDL cholesterol or triglycerides. About 7 percent got worse on at least two measures. And the researchers say they do not know why. “It is bizarre,” said Claude Bouchard, lead author of the paper , published on Wednesday in the journal PLoS One . . . Dr. Michael Lauer, director of the Division of Cardiovascular Sciences at the National Heart, Lung, and Blood Institute, the lead federal
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