Adds confidence interval for the index of mediation to a model
fitted with mdt_simple
.
# S3 method for class 'simple_mediation'
add_index(mediation_model, times = 5000, level = 0.05, ...)
Indirect effect index for simple mediation uses a and b estimates and their standard errors to compute the ab product distribution using Monte Carlo methods (see MacKinnon, Lockwood, & Williams, 2004).
MacKinnon, D. P., Lockwood, C. M., & Williams, J. (2004). Confidence Limits for the Indirect Effect: Distribution of the Product and Resampling Methods. Multivariate Behavioral Research, 39(1), 99-128. doi: 10.1207/s15327906mbr3901_4
## getting an indirect effect index
ho_et_al$condition_c <- build_contrast(ho_et_al$condition,
"Low discrimination",
"High discrimination")
simple_model <- mdt_simple(data = ho_et_al,
IV = condition_c,
DV = hypodescent,
M = linkedfate)
add_index(simple_model)
#> Test of mediation (simple mediation)
#> ==============================================
#>
#> Variables:
#>
#> - IV: condition_c
#> - DV: hypodescent
#> - M: linkedfate
#>
#> Paths:
#>
#> ==== ============== ===== =======================
#> Path Point estimate SE APA
#> ==== ============== ===== =======================
#> a 0.772 0.085 t(822) = 9.10, p < .001
#> b 0.187 0.033 t(821) = 5.75, p < .001
#> c 0.171 0.081 t(822) = 2.13, p = .034
#> c' 0.027 0.083 t(821) = 0.33, p = .742
#> ==== ============== ===== =======================
#>
#> Indirect effect index:
#>
#> - type: Indirect effect
#> - point estimate: 0.144
#> - confidence interval:
#> - method: Monte Carlo (5000 iterations)
#> - level: 0.05
#> - CI: [0.0896; 0.208]
#>
#> Fitted models:
#>
#> - X -> Y
#> - X -> M
#> - X + M -> Y