es_variab_from_means_sd {metaConvert}

Convert means and/or standard deviations of two independent groups into two effect measures (VR/CVR)

Description

Convert means and/or standard deviations of two independent groups into two effect measures (VR/CVR)

Usage

es_variab_from_means_sd(
  mean_exp,
  mean_nexp,
  mean_sd_exp,
  mean_sd_nexp,
  n_exp,
  n_nexp,
  reverse_means_variability
)

Arguments

mean_exp

mean of participants in the experimental/exposed group.

mean_nexp

mean of participants in the non-experimental/non-exposed group.

mean_sd_exp

standard deviation of participants in the experimental/exposed group.

mean_sd_nexp

standard deviation of participants in the non-experimental/non-exposed group.

n_exp

number of participants in the experimental/exposed group.

n_nexp

number of participants in the non-experimental/non-exposed group.

reverse_means_variability

a logical value indicating whether the direction of the generated effect sizes should be flipped.

Details

This function converts the means and standard deviations of two independent groups into a log variability ratio (VR) and a log coefficient of variation ratio (CVR).

The formulas used to obtain the log VR are (formulas 5 and 15, Senior et al. 2020):

logvr = log(\frac{mean\_sd\_exp}{mean\_sd\_nexp}) + \frac{1}{2 * (n\_exp - 1)} - \frac{1}{2 * (n\_nexp - 1)}

logvr\_se = \sqrt{\frac{1}{2 * (n\_exp - 1)} + \frac{1}{2 * (n\_nexp - 1)}}

logvr\_ci\_lo = logvr - qnorm(.975) * logvr\_se

logvr\_ci\_up = logvr + qnorm(.975) * logvr\_se

The formulas used to obtain the log CVR are (formulas 6 and 16, Senior et al. 2020):

cvt = mean\_sd\_exp / mean\_exp

cvc = mean\_sd\_nexp / mean\_nexp

logcvr = log(\frac{cvt}{cvc}) + \frac{1}{2} * (\frac{1}{n\_exp - 1} - \frac{1}{n\_nexp - 1}) + \frac{1}{2} * (\frac{mean\_sd\_nexp^2}{n\_nexp * mean\_nexp^2} - \frac{mean\_sd\_exp^2}{n\_exp * mean\_exp^2})

vt\_exp = \frac{mean\_sd\_exp^2}{n\_exp * mean\_exp^2} + \frac{mean\_sd\_exp^4}{2 * n\_exp^2 * mean\_exp^4} + \frac{n\_exp}{(n\_exp - 1)^2}

vt\_nexp = \frac{mean\_sd\_nexp^2}{n\_nexp * mean\_nexp^2} + \frac{mean\_sd\_nexp^4}{2 * n\_nexp^2 * mean\_nexp^4} + \frac{n\_nexp}{(n\_nexp - 1)^2}

logcvr\_se = \sqrt{vt\_exp + vt\_nexp}

logcvr\_ci\_lo = logcvr - qnorm(.975) * logcvr\_se

logcvr\_ci\_up = logcvr + qnorm(.975) * logcvr\_se

Value

This function estimates VR and CVR

natural effect size measure	VR + CVR
converted effect size measure	No conversion performed
required input data	See 'Section 23. User's input (crude)'
	https://metaconvert.org/html/input.html

References

Senior, A. M., Viechtbauer, W., & Nakagawa, S. (2020). Revisiting and expanding the meta-analysis of variation: The log coefficient of variation ratio. Research Synthesis Methods, 11(4), 553-567. https://doi.org/10.1002/jrsm.1423

Examples

es_variab_from_means_sd(
  n_exp = 55, n_nexp = 55,
  mean_exp = 2.3, mean_sd_exp = 1.2,
  mean_nexp = 1.9, mean_sd_nexp = 0.9
)