Table 1.
Simulation statistics of the estimated natural indirect effect for a continuous exposure and a dichotomous outcome, n = 200.
Scenario | True Y Model | True M Model | Risk Difference, IE(x)RD (%) |
Odds Ratio, log(IE(x)OR) |
||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
True IE | Ave Est IE | Ave PE (%) | SD of Est IE | AVE SE | CP (%) | True log(IE) | Ave Est log(IE) | Ave PE (%) | SD of Est log(IE) | AVE SE | CP (%) | |||
Binary Mediator | ||||||||||||||
1 | Logit | Logit | 1.07 | 1.09 | 1.7 | 0.67 | 0.66 | 91.1 | 0.068 | 0.069 | 2.1 | 0.041 | 0.040 | 91.1 |
2 | Logit | Probit | 0.81 | 0.84 | 4.4 | 0.61 | 0.59 | 92.7 | 0.051 | 0.053 | 3.8 | 0.037 | 0.036 | 92.8 |
3 | Probit | Logit | 0.74 | 0.78 | 5.2 | 0.57 | 0.56 | 91.1 | 0.047 | 0.049 | 4.6 | 0.035 | 0.035 | 91.9 |
4 | Probit | Probit | 0.82 | 0.86 | 5.8 | 0.60 | 0.60 | 93.6 | 0.052 | 0.054 | 4.1 | 0.036 | 0.037 | 93.6 |
Continuous Mediator | ||||||||||||||
5 | Logit | Lin† | 0.85 | 0.83 | −2.0 | 0.50 | 0.51 | 91.5 | 0.046 | 0.046 | −1.0 | 0.027 | 0.028 | 92.6 |
6 | Logit | Mix† | 0.71 | 0.64 | −9.1 | 0.53 | 0.52 | 92.5 | 0.038 | 0.034 | −8.8 | 0.028 | 0.027 | 92.9 |
7 | Probit | Lin† | 0.88 | 0.92 | 5.6 | 0.57 | 0.54 | 93.0 | 0.049 | 0.052 | 5.9 | 0.031 | 0.030 | 93.3 |
8 | Probit | Mix† | 0.87 | 0.81 | −7.4 | 0.64 | 0.64 | 93.1 | 0.042 | 0.039 | −7.4 | 0.030 | 0.030 | 93.7 |
Lin, a linear regression model for the continuous mediator M with normally distributed residuals; Mix, a Gaussian mixture model for the continuous mediator M with a weighted sum of two Gaussian component densities.