andrew_gelman_stats andrew_gelman_stats-2012 andrew_gelman_stats-2012-1356 knowledge-graph by maker-knowledge-mining
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Introduction: 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 to question 20 From yesterday : 20. Explain in two sentences why we expect survey respondents to be honest about vote preferences but possibly dishonest about reporting unhealty behaviors. Solution: Respondents tend to be sincere about vote preferences because this affects the outcome of the poll, and people are motivated to have their candidate poll well. This motivation is typically not present in reporting behaviors; you have no particular reason for wanting to affect the average survey response.
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same-blog 1 1.0 1356 andrew gelman stats-2012-05-31-Question 21 of my final exam for Design and Analysis of Sample Surveys
Introduction: 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 to question 20 From yesterday : 20. Explain in two sentences why we expect survey respondents to be honest about vote preferences but possibly dishonest about reporting unhealty behaviors. Solution: Respondents tend to be sincere about vote preferences because this affects the outcome of the poll, and people are motivated to have their candidate poll well. This motivation is typically not present in reporting behaviors; you have no particular reason for wanting to affect the average survey response.
2 0.37910044 1358 andrew gelman stats-2012-06-01-Question 22 of my final exam for Design and Analysis of Sample Surveys
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
3 0.23804678 389 andrew gelman stats-2010-11-01-Why it can be rational to vote
Introduction: I think I can best do my civic duty by running this one every Election Day, just like Art Buchwald on Thanksgiving. . . . With a national election coming up, and with the publicity at its maximum, now is a good time to ask, is it rational for you to vote? And, by extension, wass it worth your while to pay attention to whatever the candidates and party leaders have been saying for the year or so? With a chance of casting a decisive vote that is comparable to the chance of winning the lottery, what is the gain from being a good citizen and casting your vote? The short answer is, quite a lot. First the bad news. With 100 million voters, your chance that your vote will be decisive–even if the national election is predicted to be reasonably close–is, at best, 1 in a million in a battleground district and much less in a noncompetitive district such as where I live. (The calculation is based on the chance that your district’s vote will be exactly tied, along with the chance that your di
4 0.23804678 1565 andrew gelman stats-2012-11-06-Why it can be rational to vote
Introduction: I think I can best do my civic duty by running this one every Election Day, just like Art Buchwald on Thanksgiving. . . . With a national election coming up, and with the publicity at its maximum, now is a good time to ask, is it rational for you to vote? And, by extension, wass it worth your while to pay attention to whatever the candidates and party leaders have been saying for the year or so? With a chance of casting a decisive vote that is comparable to the chance of winning the lottery, what is the gain from being a good citizen and casting your vote? The short answer is, quite a lot. First the bad news. With 100 million voters, your chance that your vote will be decisive–even if the national election is predicted to be reasonably close–is, at best, 1 in a million in a battleground district and much less in a noncompetitive district such as where I live. (The calculation is based on the chance that your district’s vote will be exactly tied, along with the chance that you
5 0.20545733 1353 andrew gelman stats-2012-05-30-Question 20 of my final exam for Design and Analysis of Sample Surveys
Introduction: 20. Explain in two sentences why we expect survey respondents to be honest about vote preferences but possibly dishonest about reporting unhealty behaviors. Solution to question 19 From yesterday : 19. A survey is taken of students in a metropolitan area. At the first stage a school is sampled at random. The schools are divided into two strata: 20 private schools and 50 public schools are sampled. At the second stage, 5 classes are sampled within each sampled school. At the third stage, 10 students are sampled within each class. What is the probability that any given student is sampled? Express this in terms of the number of students in the class, number of classes in the school, and number of schools in the area. Define appropriate notation as needed. Solution: Probability a student is sampled is A*B*C, where A = 20/(# private schools) if the student is at a private school, or 50/(# public schools) if the student is at a public school, B = 5/(# classes in the student
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same-blog 1 0.99066699 1356 andrew gelman stats-2012-05-31-Question 21 of my final exam for Design and Analysis of Sample Surveys
Introduction: 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 to question 20 From yesterday : 20. Explain in two sentences why we expect survey respondents to be honest about vote preferences but possibly dishonest about reporting unhealty behaviors. Solution: Respondents tend to be sincere about vote preferences because this affects the outcome of the poll, and people are motivated to have their candidate poll well. This motivation is typically not present in reporting behaviors; you have no particular reason for wanting to affect the average survey response.
2 0.81319016 1358 andrew gelman stats-2012-06-01-Question 22 of my final exam for Design and Analysis of Sample Surveys
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
3 0.75830418 1320 andrew gelman stats-2012-05-14-Question 4 of my final exam for Design and Analysis of Sample Surveys
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.
4 0.75718659 1313 andrew gelman stats-2012-05-11-Question 1 of my final exam for Design and Analysis of Sample Surveys
Introduction: 1. Suppose that, in a survey of 1000 people in a state, 400 say they voted in a recent primary election. Actually, though, the voter turnout was only 30%. Give an estimate of the probability that a nonvoter will falsely state that he or she voted. (Assume that all voters honestly report that they voted.) P.S. The commenters are picking up some of the unintended “Hare and pineapple” ambiguity in my question!
5 0.74937427 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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1 0.98665869 577 andrew gelman stats-2011-02-16-Annals of really really stupid spam
Introduction: This came in the inbox today: Dear Dr. Gelman, GenWay recently found your article titled “Multiple imputation for model checking: completed-data plots with missing and latent data.” (Biometrics. 2005 Mar;61(1):74-85.) and thought you might be interested in learning about our superior quality signaling proteins. GenWay prides itself on being a leader in customer service aiming to exceed your expectations with the quality and price of our products. With more than 60,000 reagents backed by our outstanding guarantee you are sure to find the products you have been searching for. Please feel free to visit the following resource pages: * Apoptosis Pathway (product list) * Adipocytokine (product list) * Cell Cycle Pathway (product list) * Jak STAT (product list) * GnRH (product list) * MAPK (product list) * mTOR (product list) * T Cell Receptor (product list) * TGF-beta (product list) * Wnt (product list) * View All Pathways
2 0.97591829 993 andrew gelman stats-2011-11-05-The sort of thing that gives technocratic reasoning a bad name
Introduction: 1. Freakonomics characterizes drunk driving as an example of “the human tendency to worry about rare problems that are unlikely to happen.” 2. The CDC reports , “Alcohol-impaired drivers are involved in about 1 in 3 crash deaths, resulting in nearly 11,000 deaths in 2009.” No offense to the tenured faculty at the University of Chicago, but I’m going with the CDC on this one. P.S. The Freakonomics blog deserves to be dinged another time, not just for claiming, based on implausible assumptions and making the all-else-equal fallacy that “drunk walking is 8 times more likely to result in your death than drunk driving” but for presenting this weak inference as a fact rather than as a speculation. When doing “Freakonomics,” you can be counterintuitive, or you can be sensible, but it’s hard to be both. I mean, sure, sometimes you can be. But there’s a tradeoff, and in this case, they’re choosing to push the envelope on counterintuitiveness.
same-blog 3 0.96678919 1356 andrew gelman stats-2012-05-31-Question 21 of my final exam for Design and Analysis of Sample Surveys
Introduction: 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 to question 20 From yesterday : 20. Explain in two sentences why we expect survey respondents to be honest about vote preferences but possibly dishonest about reporting unhealty behaviors. Solution: Respondents tend to be sincere about vote preferences because this affects the outcome of the poll, and people are motivated to have their candidate poll well. This motivation is typically not present in reporting behaviors; you have no particular reason for wanting to affect the average survey response.
4 0.93539846 1332 andrew gelman stats-2012-05-20-Problemen met het boek
Introduction: Regarding the so-called Dutch Book argument for Bayesian inference (the idea that, if your inferences do not correspond to a Bayesian posterior distribution, you can be forced to make incoherent bets and ultimately become a money pump), I wrote: I have never found this argument appealing, because a bet is a game not a decision. A bet requires 2 players, and one player has to offer the bets. I do agree that in some bounded settings (for example, betting on win place show in a horse race), I’d want my bets to be coherent; if they are incoherent (e.g., if my bets correspond to P(A|B)*P(B) not being equal to P(A,B)), then I should be able to do better by examining the incoherence. But in an “open system” (to borrow some physics jargon), I don’t think coherence is possible. There is always new information coming in, and there is always additional prior information in reserve that hasn’t entered the model.
5 0.9270516 1532 andrew gelman stats-2012-10-13-A real-life dollar auction game!
Introduction: Actually, $100,000 auction. I learned about it after seeing the following email which was broadcast to a couple of mailing lists: Dear all, I am now writing about something completely different! I need your help “voting” for our project, and sending this e-mail to others so that they can also vote for our project. As you will see from the video, the project would fund *** Project: I am a finalist for a $100,000 prize from Brigham and Women’s Hospital. My project is to understand how ***. Ultimately, we want to develop a ***. We expect that this ** can be used to *** Here are the instructions: 1. Go to the web page: http://brighamandwomens.org/research/BFF/default.aspx 2. scroll to the bottom and follow the link to “Vote” 3. select project #** 4. FORWARD THIS E-MAIL TO AS MANY PEOPLE AS YOU CAN. Best regards, ** I love that step 4 is in ALL CAPS, just to give it that genuine chain-letter aura. Isn’t this weird? First, that this foundation would give ou
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