bsummary {brmsmargins}

Personal Preference Based Bayesian Summary

Description

Returns a summary of a posterior distribution for a single parameter / value. It is based on personal preference. Notably, it does not only use bayestestR::describe_posterior, an excellent function, because of the desire to also describe the percentage of the full posterior distribution that is at or exceeding the value of a Minimally Important Difference (MID). MIDs are used in clinical studies with outcome measures where there are pre-defined differences that are considered clinically important, which is distinct from the ROPE or general credible intervals capturing uncertainty.

Usage

bsummary(x, CI = 0.99, CIType = "HDI", ROPE = NULL, MID = NULL)

Arguments

x

The posterior distribution of a parameter

CI

A numeric value indicating the desired width of the credible interval. Defaults to 0.99 currently, but this is subject to change. a 99% interval was chosen as the default as there have been recent arguments made in the realm of meta science that there are, essentially, too many false positives and that many of the “findings” in science are not able to be replicated. In any case, users should ideally specify a desired CI width, and not rely on defaults.

CIType

A character string indicating the type of credible interval, passed on to the ci function as the method for CIs.

ROPE

Either left as NULL, the default, or a numeric vector of length 2, specifying the lower and upper thresholds for the Region of Practical Equivalence (ROPE).

MID

Either left as NULL, the default, or a numeric vector of length 2, specifying the lower and upper thresholds for a Minimally Important Difference (MID). Unlike the ROPE, percentages for the MID are calculated as at or exceeding the bounds specified by this argument, whereas the ROPE is the percentage of the posterior at or inside the bounds specified.

Value

A data.table with the mean, M

M

the mean of the posterior samples

Mdn

the median of the posterior samples

LL

the lower limit of the credible interval

UL

the upper limit of the credible interval

PercentROPE

the percentage of posterior samples falling into the ROPE

PercentMID

the percentage of posterior samples falling at or beyond the MID

CI

the width of the credible interval used

CIType

the type of credible interval used (e.g., highest density interval)

ROPE

a label describing the values included in the ROPE

MID

a label describing the values included in the MID

References

Kruschke, J. K. (2018). doi:10.1177/2515245918771304 “Rejecting or accepting parameter values in Bayesian estimation”

Examples

bsummary(rnorm(1000))

bsummary(rnorm(1000), ROPE = c(-.5, .5), MID = c(-1, 1))