Estimate Cohen's d corresponding to a Meaningful Change Definition

This function uses a base rate (Control Event Rate, argument cer) and a Meaningful Change Definitions (MCD, argument mcd) to compute the corresponding Cohen's d. See Gruijters & Peters (2019) for details.

dMCD(
  cer,
  mcd = NULL,
  eer = NULL,
  plot = TRUE,
  mcdOnX = FALSE,
  plotResultValues = TRUE,
  resultValueLineColor = "blue",
  resultValueLineSize = 1,
  returnLineLayerOnly = FALSE,
  theme = ggplot2::theme_bw(),
  highestPossibleEER = 0.999999999,
  xLab = ifelse(mcdOnX, "Meaningful Change Definition", "Control Event Rate"),
  yLab = "Cohen's d",
  dist = "norm",
  distArgs = list(),
  distNS = "stats",
  ...
)

# S3 method for dMCD
print(x, ...)

Arguments

cer: The Control Event Rate (or base rate): how many people already perform the target behavior in the population (as a proportion)?
mcd: The Meaningful Change Definitions: by which percentage (as a proportion) should the event rate increase to render an effect meaningful?
eer: Instead of the MCD, it is also possible to specify the Experimental Event Rate (EER), in which case the MCD is computed by taking the difference with the CER.
plot: Whether to show a plot.
mcdOnX: Whether to plot the Meaningful Change Definition on the X axis (by default, the CER is plotted on the X axis).
plotResultValues: Whether to plot the result values.
resultValueLineColor, resultValueLineSize: If plotting the result values, lines of this color and size are used.
returnLineLayerOnly: Whether to only return a layer with the plotted line (which can be used to quickly stack lines for different MCDs).
theme: The ggplot2 theme to use.
highestPossibleEER: The highest possible EER to include in the plot.
xLab, yLab: The labels for the X and Y axes.
dist, distArgs, distNS: Used to specify the distribution to use to convert between Cohen's d and the CER and EER. distArgs can be used to specify additional arguments to the corresponding q and p functions, and distNS to specify the namespace (i.e. package) from where to get the distribution functions.
...: Any additional arguments to dMCD are passed on to the ggplot2::geom_line used to draw the line showing the different Cohen's d values as a function of the base rate (or MCD) on the X axis. Additional arguments for the print method are passed on to the default print method.
x: The object to print (i.e. a result from a call to dMCD).

Value

The Cohen's d value, optionally with a ggplot2 plot stored in an attribute (which is only a ggplot2 layer if returnLineLayerOnly=TRUE).

References

Gruijters, S. L. K., & Peters, G.-J. Y. (2020). Meaningful change definitions: Sample size planning for experimental intervention research. PsyArXiv. doi: 10.31234/osf.io/jc295

Examples

dMCD(.2, .05);
#>      mcd
#> cer        0.05
#>   0.2 0.1671315