dSep: Tests of directed separation

In piecewiseSEM: Piecewise Structural Equation Modeling

Tests of directed separation

Description

Evaluation of conditional independence claims to be used in determining the goodness-of-fit for piecewise structural equation models.

Usage

dSep(
  modelList,
  basis.set = NULL,
  direction = NULL,
  interactions = FALSE,
  conserve = FALSE,
  conditioning = FALSE,
  .progressBar = TRUE
)

Arguments

modelList	A list of structural equations created using psem.
basis.set	An optional list of independence claims.
direction	A vector of claims defining the specific directionality of independence claims; for use in special cases (see Details).
interactions	whether interactions should be included in independence claims. Default is FALSE
conserve	Whether the most conservative P-value should be returned; for use in special cases (see Details). Default is FALSE.
conditioning	Whether the conditioning variables should be shown in the summary table. Default is FALSE.
.progressBar	An optional progress bar. Default is TRUE.

Details

In cases involving non-normally distributed responses in the independence claims that are modeled using generalized linear models, the significance of the independence claim is not reversible (e.g., the P-value of Y ~ X is not the same as X ~ Y). This is due to the transformation of the response via the link function. In extreme cases, this can bias the goodness-of-fit tests. summary.psem will issue a warning when this case is present and provide guidance for solutions.

One solution is to specify the directionality of the relationship using the direction argument, e.g. direction = c("X <- Y"). Another is to run both tests (Y ~ X, X ~ Y) and return the most conservative (i.e., lowest) P-value, which can be toggled using the conserve = TRUE argument.

Value

Returns a data.frame of independence claims and their significance values.

Author(s)

Jon Lefcheck <[e-mail]>, Jarrett Byrnes

References

Shipley, Bill. "A new inferential test for path models based on directed acyclic graphs." Structural Equation Modeling 7.2 (2000): 206-218.

See Also

basisSet

piecewiseSEM documentation built on June 22, 2024, 9:53 a.m.