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posted by n1 on Monday November 17 2014, @10:34PM   Printer-friendly
from the statistical-significance dept.

Stanford research reaffirms that right-to-carry gun laws are connected with an increase in violent crime. This debunks – with the latest empirical evidence – earlier claims that more guns actually lead to less crime.

While there is no federal law on concealed-carry permits, all 50 states have passed laws allowing citizens to carry certain concealed firearms in public, either without a permit or after obtaining a permit from local government or law enforcement.

Recently published scholarship updates the empirical evidence on this issue. Stanford law Professor John J. Donohue III, Stanford law student Abhay Aneja and doctoral student Alexandria Zhang from Johns Hopkins University were the co-authors of the study.

[Abstract]: http://papers.ssrn.com/sol3/papers.cfm?abstract_id=2443681

 
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  • (Score: 5, Informative) by physicsmajor on Monday November 17 2014, @11:49PM

    by physicsmajor (1471) on Monday November 17 2014, @11:49PM (#117003)

    tl;dr up front: This study is completely without value. There is literally nothing to see here. What you're about to read would be failed out of high school statistics, and the authors should be downright ashamed. I'm going to paste the abstract here and tear it apart paragraph by paragraph below, as should any objective, scientific observer demanding good, evidence-based findings, but you can skip that now. Seriously, save your time. I've wasted mine instead.

    For over a decade, there has been a spirited academic debate over the impact on crime of laws that grant citizens the presumptive right to carry concealed handguns in public – so-called right-to-carry (RTC) laws. In 2004, the National Research Council (NRC) offered a critical evaluation of the “More Guns, Less Crime” hypothesis using county-level crime data for the period 1977-2000. 15 of the 16 academic members of the NRC panel essentially concluded that the existing research was inadequate to conclude that RTC laws increased or decreased crime. One member of the panel thought the NRC's panel data regressions showed that RTC laws decreased murder, but the other 15 responded by saying that “the scientific evidence does not support” that position.

    Authors tip their bias in the first sentence using non-professional language like "so-called" instead of the proper "hereafter referred to [by their common title]" or similar. They then attempt to conflate the very stable majority position (15/16), based on the actual statistical analysis at the time, with opinion instead of established fact using words like "saying," and again tip their hands in the last sentence by stating the outlier's position first, then getting to "the other 15." Not a good start, guys. Maybe for mainstream news, but if you want to be taken seriously I've already binned your credibility with CNN or Fox News. However, let's continue.

    We evaluate the NRC evidence, and improve and expand on the report’s county data analysis by analyzing an additional six years of county data as well as state panel data for the period 1979-2010. We also present evidence using both a more plausible version of the Lott and Mustard specification, as well as our own preferred specification (which, unlike the Lott and Mustard model presented in the NRC report, does control for rates of incarceration and police). While we have considerable sympathy with the NRC’s majority view about the difficulty of drawing conclusions from simple panel data models and re-affirm its finding that the conclusion of the dissenting panel member that RTC laws reduce murder has no statistical support, we disagree with the NRC report’s judgment on one methodological point: the NRC report states that cluster adjustments to correct for serial correlation are not needed in these panel data regressions, but our randomization tests show that without such adjustments the Type 1 error soars to 22-73 percent.

    So they re-analyze with additional data. Why not lead with that, instead of the biased prior paragraph? They then claim their model is better - wait, no, they don't actually claim superiority at all but that theirs is preferred. By whom? Themselves, one assumes. They then "sympathize" with the majority view but claim their findings lie with the single dissenter, again attempting to soften or opinion-ify what should be based on hard evidence alone. Where is theirs? That bit appears to be 100% opinion. The last sentence appears to be FUD about Type 1 error - potentially relevant, but they don't bother to explain why or how. "Blah blah we screwed with the data and made up reasons for why we needed to" appears to be what's going on here. Even if relevant, this is only useful for those who have read and are intimately familiar with the prior study - which is not the place for an abstract. Abstracts should stand alone.

    Our paper highlights some important questions to consider when using panel data methods to resolve questions of law and policy effectiveness. We buttress the NRC’s cautious conclusion regarding the effects of RTC laws by showing how sensitive the estimated impact of RTC laws is to different data periods, the use of state versus county data, particular specifications (especially the Lott-Mustard inclusion of 36 highly collinear demographic variables), and the decision to control for state trends.

    These sound like potentially important factors, but the chicken is coming before the egg here - they should be listed after the evidence as discussion/conclusions falling from those findings.

    Across the basic seven Index I crime categories, the strongest evidence of a statistically significant effect would be for aggravated assault, with 11 of 28 estimates suggesting that RTC laws increase this crime at the .10 confidence level. An omitted variable bias test on our preferred Table 8a results suggests that our estimated 8 percent increase in aggravated assaults from RTC laws may understate the true harmful impact of RTC laws on aggravated assault, which may explain why this finding is only significant at the .10 level in many of our models. Our analysis of the year-by-year impact of RTC laws also suggests that RTC laws increase aggravated assaults. Our analysis of admittedly imperfect gun aggravated assaults provides suggestive evidence that RTC laws may be associated with large increases in this crime, perhaps increasing such gun assaults by almost 33 percent.

    Bad start for the real evidence. They looked across all the Index I categories and the best they've got is "the strongest evidence of a statistically significant effect" which is at the 0.10 level... about half the time (11/28). Remember, folks, if you want to talk about the 0.10 level one in ten of your investigations is going to return false positive results! They flat out admit they were searching seven categories here, so I'm definitely not impressed, and neither should you be. Then they talk about their "preferred" analysis/results, and assert that danger may be understated in many of their models. Folks, this is already reading like what should be buried at the bottom of a "limitations" section. f this was so relevant, such an important effect, which spanned many of their models and is worth noting in the second sentence of your Abstract's results, you'd better damn well follow through and explore that instead of just spewing pure speculation. Then they find "suggestive" results with no actual test values noted - given they found an alpha of 0.10 worth reporting, I'm not holding my breath here. In the final sentence they weaken the inevitable brutal rebuttal of the paper by noting "admittedly imperfect" data and again use the statistical weasel words "suggestive evidence" and "perhaps" before asserting things which they obviously have no evidence to support.

    It's actually hilarious they say gun assaults could increase by almost 33% without a single mention of a significance level or test result for this claim. Is this actually a joke? Nope, there's another paragraph to go yet.

    In addition to aggravated assault, the most plausible state models conducted over the entire 1979-2010 period provide evidence that RTC laws increase rape and robbery (but usually only at the .10 level). In contrast, for the period from 1999-2010 (which seeks to remove the confounding influence of the crack cocaine epidemic), the preferred state model (for those who accept the Wolfers proposition that one should not control for state trends) yields statistically significant evidence for only one crime – suggesting that RTC laws increase the rate of murder at the .05 significance level. It will be worth exploring whether other methodological approaches and/or additional years of data will confirm the results of this panel-data analysis and clarify some of the highly sensitive results and anomalies (such as the occasional estimates that RTC laws lead to higher rates of property crime) that have plagued this inquiry for over a decade.

    More worthless statistics, needing an alpha of 0.10 to be mentioned. Any writer with a shred of integrity would mention this as incredibly suggestive and non-significant first, instead of burying the alpha level at the end in hopes the reader is too incompetent to realize they're spewing valueless assertions. Hey, finally here at the end if we limit the data range and use their "preferred" model a single crime reaches significance at an alpha of 0.05. Not stated: how many crimes were stated, or how many other models/date ranges were attempted before they found one that supported their agenda. In all likelihood this is another random finding thanks to p-hacking.

    This isn't a real study at all, just an excuse to feed politicians "scientific" ammunition for an agenda shared by the authors.

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  • (Score: 2) by Runaway1956 on Tuesday November 18 2014, @12:04AM

    by Runaway1956 (2926) Subscriber Badge on Tuesday November 18 2014, @12:04AM (#117014) Homepage Journal

    Thank you, Sir. I'm actually slowly reading through the article. I lack any training in statistics, so it's slow going for me. I think you've sliced and diced them pretty well, just based on that abstract. Gotta get my butt off to work soon - it will probably be late tomorrow before I finish reading. Depending on comments on this page, I may not even bother reading it all.

    --
    "I didn't lose to him!" - The Donald referring to Trippin' Joe
  • (Score: 1) by CyprusBlue on Tuesday November 18 2014, @02:44AM

    by CyprusBlue (943) on Tuesday November 18 2014, @02:44AM (#117080)

    I'd mod you up if I had points. This is the kind of commentary that SHOULD be on this site, by far.

  • (Score: 1) by jmorris on Tuesday November 18 2014, @07:20AM

    by jmorris (4844) on Tuesday November 18 2014, @07:20AM (#117148)

    This is so bad I wonder if this isn't some performance art stunt to study the reaction to the study, how many news outlets just run with it, if ANYBODY was going to notice the 0.10 value, etc.

    Since it has been posted for months and it didn't break into the Party Media I'd guess even they were bright enough to realize they would get embarrassed if they tried their usual tactics with this one.

    Bottom line is you don't need some overly complicated study that carefully massages the numbers until they produce a political screed under the guise of science. The Abstract gives the game away, all States have moved to liberalize RTC laws and Google will give you the other half of the equation, that violent crime is down, and down more in the areas with the more liberal carry laws. More guns, less crime; it really is that simple because RAH said it best, "An armed society is a polite society."

  • (Score: 2) by metamonkey on Tuesday November 18 2014, @06:17PM

    by metamonkey (3174) on Tuesday November 18 2014, @06:17PM (#117338)

    Thank you for doing that so I didn't have to.

    --
    Okay 3, 2, 1, let's jam.
  • (Score: 2) by FatPhil on Wednesday November 19 2014, @12:44AM

    by FatPhil (863) <pc-soylentNO@SPAMasdf.fi> on Wednesday November 19 2014, @12:44AM (#117465) Homepage
    > > 15 of the 16 academic members of the NRC panel essentially concluded that the existing research was inadequate to conclude that RTC laws increased or decreased crime. One member of the panel

    > tip their hands in the last sentence by stating the outlier's position first, then getting to "the other 15."

    Erm, but they got to the other 15 in the sentence before. Does "first" mean something different to you?
    --
    I know I'm God, because every time I pray to him, I find I'm talking to myself.
  • (Score: 2) by FatPhil on Wednesday November 19 2014, @12:52AM

    by FatPhil (863) <pc-soylentNO@SPAMasdf.fi> on Wednesday November 19 2014, @12:52AM (#117468) Homepage
    > They then "sympathize" with the majority view but claim their findings lie with the single dissenter

    But their views are quite the opposite:

    "One member of the panel thought ... RTC laws decreased murder"
    "Our analysis ... suggests that RTC laws increase aggravated assaults."

    I really don't think you are in a position to claim there are errors in their paper when you can't even understand what you read.
    --
    I know I'm God, because every time I pray to him, I find I'm talking to myself.