Summarize Posterior Distributions of Model Differences

Credible intervals are created for the differences. Also, region of practical equivalence (ROPE) statistics are computed when the effective size of a difference is given.

Usage

# S3 method for posterior_diff
summary(object, prob = 0.9, size = 0, ...)

Arguments

object

An object produced by contrast_models().

prob

A number p (0 < p < 1) indicating the desired probability mass to include in the intervals.

size

The size of an effective difference in the units of the chosen metric. For example, a 5 percent increase in accuracy (size = 0.05) between two models might be considered a "real" difference.

...

Not currently used

Value

A data frame with interval and ROPE statistics for each comparison.

Details

The ROPE estimates included in the results are the columns pract_neg, pract_equiv, and pract_pos. pract_neg integrates the portion of the posterior below -size (and pract_pos is the upper integral starting at size). The interpretation depends on whether the metric being analyzed is better when larger or smaller. pract_equiv integrates between [-size, size]. If this is close to one, the two models are unlikely to be practically different relative to size.

Examples

data("ex_objects")

summary(contrast_samples)
#> # A tibble: 2 × 9
#>   contrast probability     mean   lower  upper  size pract_neg pract_equiv
#>   <chr>          <dbl>    <dbl>   <dbl>  <dbl> <dbl>     <dbl>       <dbl>
#> 1 logisti…       1      3.29e-2  0.0196 0.0462     0        NA          NA
#> 2 logisti…       0.472 -5.40e-4 -0.0142 0.0130     0        NA          NA
#> # ℹ 1 more variable: pract_pos <dbl>
summary(contrast_samples, size = 0.025)
#> # A tibble: 2 × 9
#>   contrast probability     mean   lower  upper  size pract_neg pract_equiv
#>   <chr>          <dbl>    <dbl>   <dbl>  <dbl> <dbl>     <dbl>       <dbl>
#> 1 logisti…       1      3.29e-2  0.0196 0.0462 0.025    0            0.168
#> 2 logisti…       0.472 -5.40e-4 -0.0142 0.0130 0.025    0.0036       0.994
#> # ℹ 1 more variable: pract_pos <dbl>