Sensitivity Analyses, Average Marginal Effects Reported: Summary of Key Findings Compared with Base Probit Models
| Marginal Effect on Water-Sharing Arrangements | Marginal Effect on First Nations Water-Sharing Arrangementsa | ||
|---|---|---|---|
| First Nations water systems | Base probit model (N=145) | −0.438*** | — |
| (0.086) | |||
| Sensitivity 1: bivariate probit estimation (N=145) | −0.523*** | — | |
| (0.050) | |||
| Sensitivity 2: feasible distance Sample (N=95) | −0.382*** | — | |
| (0.074) | |||
| Sensitivity 3: addition of FNLMA variable (N=145)b | −0.439*** | — | |
| (0.093) | |||
| Municipal water systems | Base probit model (N=565) | 0.034 | — |
| (0.027) | |||
| Sensitivity 1: bivariate probit estimation (N=565) | 0.026 | — | |
| (0.040) | |||
| Sensitivity 2: feasible distance sample (N=551) | 0.031 | — | |
| (0.025) | |||
| Full sample with interaction effect | Base probit model (N=710) | −0.075** | −0.331*** |
| (0.030) | (0.086) | ||
| Sensitivity 1: bivariate probit estimation (N=710) | −0.101** | −0.348*** | |
| (0.050) | (0.091) | ||
| Sensitivity 2: feasible distance sample (N=646) | −0.042* | −0.335*** | |
| (0.024) | (0.097) |
Note: Standard errors are in parentheses and are clustered by census subdivision (i.e., community housing the water system). The dependent variable equals 1 if the drinking water advisory was in effect at some point during the study period (2009–2010), 0 otherwise.
↵a Stata does not generate marginal effects for interaction terms (in our case, i.WSA##i.FN) using the standard “margins” command. The marginal effect for this interaction term was calculated separately using the following command: margins WSA, dydx(FN) pwcompare(effects). This marginal effect compares First Nations water systems supplied through water-sharing arrangements to First Nations water systems that are independently supplied.
↵b Marginal effect from probit model specification reported; result remains consistent when the model is run as a bivariate probit. Full probit and bivariate probit results are provided in Appendix Table A2.3.
↵* p < 0.1;
↵** p < 0.05;
↵*** p < 0.01.