Evaluating Missouri's Handgun Purchaser Law: A Bracketing Method for Addressing Concerns About History Interacting with Group
| Autor: | Daniel W. Webster, Raiden B. Hasegawa, Dylan S. Small |
|---|---|
| Rok vydání: | 2019 |
| Předmět: |
Firearms
Missouri Epidemiology Group (mathematics) Causal effect Repeal 01 natural sciences Outcome (probability) Confidence interval 010104 statistics & probability 03 medical and health sciences 0302 clinical medicine Homicide Law Humans 030212 general & internal medicine 0101 mathematics Bracketing Unmeasured confounding Psychology Epidemiologic Methods |
| Zdroj: | Epidemiology (Cambridge, Mass.). 30(3) |
| ISSN: | 1531-5487 |
| Popis: | In the comparative interrupted time series design (also called the method of difference-in-differences), the change in outcome in a group exposed to treatment in the periods before and after the exposure is compared with the change in outcome in a control group not exposed to treatment in either period. The standard difference-in-difference estimator for a comparative interrupted time series design will be biased for estimating the causal effect of the treatment if there is an interaction between history in the after period and the groups; for example, there is a historical event besides the start of the treatment in the after period that benefits the treated group more than the control group. We present a bracketing method for bounding the effect of an interaction between history and the groups that arises from a time-invariant unmeasured confounder having a different effect in the after period than the before period. The method is applied to a study of the effect of the repeal of Missouri's permit-to-purchase handgun law on its firearm homicide rate. We estimate that the effect of the permit-to-purchase repeal on Missouri's firearm homicide rate is bracketed between 0.9 and 1.3 homicides per 100,000 people, corresponding to a percentage increase of 17% to 27% (95% confidence interval: 0.6, 1.7 or 11%, 35%). A placebo study provides additional support for the hypothesis that the repeal has a causal effect of increasing the rate of state-wide firearm homicides. |
| Databáze: | OpenAIRE |
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