pathway {MMRcaseselection}

Pathway case

Description

Calculation of pathway values, defined as the difference between residuals of full model and reduced model lacking the pathway variable. The larger the difference, the more a case qualifies as a pathway case suitable for the analysis of mechanisms.

Usage

pathway(full_model, reduced_model)

Arguments

full_model

Full model including covariate of interest (= pathway variable)

reduced_model

Reduced model excluding covariate of interest

Details

The difference between the absolute residuals of the full and reduced model follows the approach developed by Weller and Barnes (2014): Finding Pathways: Mixed-Method Research for Studying Causal Mechanisms. Cambridge: Cambridge University Press. https://doi.org/10.1017/CBO9781139644501).

The calculation of the absolute difference between the full-model and reduced-model residuals, given a case's reduced-model residual is larger than its full-model residual, follows the proposal by Gerring (2007): Is There a (Viable) Crucial-Case Method? Comparative Political Studies 40 (3): 231-253. https://journals.sagepub.com/doi/10.1177/0010414006290784)

Value

A dataframe with

- all full model variables,

- full model residuals (full_resid),

- reduced model residuals (reduced_resid),

- pathway values following Weller/Barnes (pathway_wb),

- pathway values following Gerring (pathway_gvalue),

- variable showing whether Gerring's criterion for a pathway case is met (pathway_gstatus)

Examples

df_full <- lm(mpg ~ disp + wt, data = mtcars)
df_reduced <- lm(mpg ~ wt, data = mtcars)
pathway(df_full, df_reduced)