andrew_gelman_stats andrew_gelman_stats-2010 andrew_gelman_stats-2010-145 knowledge-graph by maker-knowledge-mining
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Introduction: Megan Price wrote in that she and Daniel Guzmán of the Benetech Human Rights Program released a paper today entitled “Comments to the article ‘Is Violence Against Union Members in Colombia Systematic and Targeted?’” (o aqui en español), which examines an article written by Colombian academics Daniel Mejía and María José Uribe. Price writes [in the third person]: The paper reviewed by Price and Guzmán concluded that “. . . on average, violence against unionists in Colombia is neither systematic nor targeted.” However, in their response, Price and Guzmán present – in technical and methodological detail – the reasons they find the conclusions in Mejía and Uribe’s study to be overstated. Price and Guzmán believe that weaknesses in the data, in the choice of the statistical model, and the interpretation of the model used in Mejía and Uribe’s study, all raise serious questions about the authors’ strong causal conclusions. Price and Guzmán point out that unchecked, those conclusio
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1 on average, violence against unionists in Colombia is neither systematic nor targeted. [sent-6, score-0.35]
2 ” However, in their response, Price and Guzmán present – in technical and methodological detail – the reasons they find the conclusions in Mejía and Uribe’s study to be overstated. [sent-7, score-0.214]
3 Price and Guzmán believe that weaknesses in the data, in the choice of the statistical model, and the interpretation of the model used in Mejía and Uribe’s study, all raise serious questions about the authors’ strong causal conclusions. [sent-8, score-0.228]
4 Price and Guzmán point out that unchecked, those conclusions may distort the truth about violence against unions and can mislead important social, economic and political decisions in Colombia. [sent-9, score-0.38]
5 They welcome the opportunity to have a methodological rather than ideological debate about union violence. [sent-10, score-0.586]
6 The public debate about union violence intensified from 2008 to 2010 as countries negotiating free trade agreements with Colombia, including the U. [sent-11, score-0.902]
7 , explicitly cited union violence as an obstacle to finalizing agreements. [sent-13, score-0.796]
8 Given the importance of this debate, any study that makes claims about the patterns and magnitude of union violence in Colombia requires the highest level of precision and scientific rigor. [sent-14, score-0.945]
9 Based on careful review and critique, Price and Guzmán conclude that Mejía and Uribe’s study does not resolve the question, “is violence against union members in Colombia systematic and targeted? [sent-15, score-0.974]
10 The Mejía and Uribe study uses convenience sample data as the basis for its claims. [sent-17, score-0.152]
11 These data are based on available, observable reports on union homicides and union activity which have been collected without a scientific random selection method. [sent-18, score-1.226]
12 These data cannot be relied upon to represent an underlying larger population or to accurately describe patterns over time and space. [sent-19, score-0.084]
13 The statistical methods used in the Mejía and Uribe study to evaluate the relationship between union homicides and “union activity” are based on commonly used least squares regression and instrumental variables analyses. [sent-21, score-0.936]
14 However, we do not believe that the study adequately addresses the data’s potential violations of these assumptions and the potential ramifications on the estimates when these assumptions are violated. [sent-23, score-0.454]
15 Violations of these assumptions could change the magnitude of parameter estimates (used to quantify the relationship between union activity and union violence) and the significance of parameter estimates (used to determine the presence or absence of any relationship). [sent-24, score-1.338]
16 One of the main modeling assumptions which we believe these data violate, uncorrelated errors, has a direct affect on significance tests used in the Mejía and Uribe study. [sent-26, score-0.292]
17 Therefore we are highly skeptical about the reliability of the conclusion that union activity and union violence are not significantly associated. [sent-27, score-1.34]
18 The descriptive and analytic results presented in Mejía and Uribe’s study indicate that union member homicide rate is a highly variable outcome measure. [sent-29, score-0.617]
19 We find that control variables in the various model formulations show inconsistent and indeed reversed effects, suggesting problems with the model specification, with the data on homicides, or both. [sent-31, score-0.168]
20 The poor quality of these models, the unknown under-registration inherent in the data, and the questionable modeling decisions, mean that the strong conclusions in Mejía and Uribe’s study are unsupported by the analyses. [sent-32, score-0.349]
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Introduction: Megan Price wrote in that she and Daniel Guzmán of the Benetech Human Rights Program released a paper today entitled “Comments to the article ‘Is Violence Against Union Members in Colombia Systematic and Targeted?’” (o aqui en español), which examines an article written by Colombian academics Daniel Mejía and María José Uribe. Price writes [in the third person]: The paper reviewed by Price and Guzmán concluded that “. . . on average, violence against unionists in Colombia is neither systematic nor targeted.” However, in their response, Price and Guzmán present – in technical and methodological detail – the reasons they find the conclusions in Mejía and Uribe’s study to be overstated. Price and Guzmán believe that weaknesses in the data, in the choice of the statistical model, and the interpretation of the model used in Mejía and Uribe’s study, all raise serious questions about the authors’ strong causal conclusions. Price and Guzmán point out that unchecked, those conclusio
Introduction: Mike Spagat sends in an interesting explanation for the noted problems with conflict mortality studies (a topic we’ve discussed on occasion on this blog). Spagat writes: This analysis is based on the fact that conflict violence does not spread out at all uniformly across a map but, rather, tends to concentrate in a few areas. This means that small, headline-grabbing violence surveys are extremely unreliable. There is a second point, based on the work of David Hemenway which you’ve also cited on your blog. Even within exceptionally violent environments most households will still not have a violent death. So a very small false positive rate in a household survey will cause substantial upward bias in violence estimates.
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Introduction: Grazia Pittau, Roberto Zelli, and I came out with a paper investigating the role of economic variables in predicting regional disparities in reported life satisfaction of European Union citizens. We use multilevel modeling to explicitly account for the hierarchical nature of our data, respondents within regions and countries, and for understanding patterns of variation within and between regions. Here’s what we found: - Personal income matters more in poor regions than in rich regions, a pattern that still holds for regions within the same country. - Being unemployed is negatively associated with life satisfaction even after controlled for income variation. Living in high unemployment regions does not alleviate the unhappiness of being out of work. - After controlling for individual characteristics and modeling interactions, regional differences in life satisfaction still remain. Here’s a quick graph; there’s more in the article:
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Introduction: In the annals of hack literature, it is sometimes said that if you aim to write best-selling crap, all you’ll end up with is crap. To truly produce best-selling crap, you have to have a conviction, perhaps misplaced, that your writing has integrity. Whether or not this is a good generalization about writing, I have seen an analogous phenomenon in statistics: If you try to do nothing but model the data, you can be in for a wild and unpleasant ride: real data always seem to have one more twist beyond our ability to model (von Neumann’s elephant’s trunk notwithstanding). But if you model the underlying process, sometimes your model can fit surprisingly well as well as inviting openings for future research progress.
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