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From |
Serena Masino <[email protected]> |

To |
"[email protected]" <[email protected]> |

Subject |
st: Rbounds- interpretation of results |

Date |
Wed, 20 Nov 2013 16:19:55 +0000 |

Hi, I am writing to enquire regarding the interpretation of rbounds results. When I run the rbounds test in STATA (after psmatch2), the output reports both the p-values from the Wilcoxon sign rank test and the Hodges-Lehman confidence intervals. I am unclear on whether we care only about the Gamma value where the ATT bounds in the first two columns in the table below become insignificant at the 95% level (I am only interested in the upper bound anyway) . Or whether the Hodges-Lehman confidence interval (last two columns in the table below) has to encompass zero when the situation just described happens. In other words: when the upper bound estimate crosses the acceptable significance level, does this also have to correspond to a Hodges-Lehman confidence interval encompassing zero? Or do we simply care about the value of Gamma at which the upper bound p-value in column 1 is >0.05? I ask, because, as you can see below, in my case, the Gamma at which the p val is >0.05 is around1.5. Because this is lower than 2, it should indicate the results are not too robust. However, at that gamma value, the corresponding Hodges-Lehman confidence interval does not encompass zero. Does that mean I should not worry about hidden bias? . rbounds delta3, gamma(1(0.1)2) alpha(.90) Rosenbaum bounds for delta3 (N = 810 matched pairs) Gamma sig+ sig- t-hat+ t-hat- CI+ CI- 1 .000053 .000053 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 1.1 .000595 3.1e-06 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 1.2 .0038 1.6e-07 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 1.3 .015868 7.2e-09 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 1.4 .047676 3.0e-10 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 1.5 .110641 1.1e-11 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 1.6 .209409 4.1e-13 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 1.7 .337338 1.4e-14 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 1.8 .47863 4.4e-16 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 1.9 .615128 0 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 2 .732844 0 -3.1e-07 -3.1e-07 -3.1e-07 -3.1e-07 * gamma - log odds of differential assignment due to unobserved factors sig+ - upper bound significance level sig- - lower bound significance level t-hat+ - upper bound Hodges-Lehmann point estimate t-hat- - lower bound Hodges-Lehmann point estimate CI+ - upper bound confidence interval (a= .9) CI- - lower bound confidence interval (a= .9) Any help on this would be greatly appreciated. Serena Masino * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

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