es_from_med_quarts {metaConvert}

Convert median and interquartile range of two independent groups into several effect size measures

Description

Convert median and interquartile range of two independent groups into several effect size measures

Usage

es_from_med_quarts(
  q1_exp,
  med_exp,
  q3_exp,
  n_exp,
  q1_nexp,
  med_nexp,
  q3_nexp,
  n_nexp,
  smd_to_cor = "viechtbauer",
  reverse_med
)

Arguments

q1_exp

first quartile of the experimental/exposed group.

med_exp

median value of the experimental/exposed group.

q3_exp

third quartile of the experimental/exposed group.

n_exp

number of participants in the experimental/exposed group.

q1_nexp

first quartile of the non-experimental/non-exposed group.

med_nexp

median value of the non-experimental/non-exposed group.

q3_nexp

third quartile of the non-experimental/non-exposed group.

n_nexp

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

smd_to_cor

formula used to convert the generated cohen_d value into a coefficient correlation (see details).

reverse_med

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

Details

This function first converts a Cohen's d (D), Hedges' g (G) and mean difference (MD) from the medians and interquartile ranges of two independent groups. Odds ratio (OR) and correlation coefficients (R/Z) are then converted from the Cohen's d.

This function recreates means+SD of the two groups (Wan et al., 2014):

mean\_exp = \frac{q1\_exp + med\_exp + q3\_exp}{3}

mean\_nexp = \frac{q1\_nexp + med\_nexp + q3\_nexp}{3}

mean\_sd\_exp = \frac{q3\_exp - q1\_exp}{2*qnorm(\frac{0.75*n\_exp - 0.125}{n\_exp+0.25})}

mean\_sd\_nexp = \frac{q3\_nexp - q1\_nexp}{2*qnorm(\frac{0.75*n\_nexp - 0.125}{n\_nexp+0.25})}

Note that if the group sample size is inferior to 50, a correction is applied to estimate the standard deviation.

From these means+SD, the function computes MD, D and G using formulas described in es_from_means_sd().

To estimate other effect size measures, calculations of the es_from_cohen_d() are applied.

Value

This function estimates and converts between several effect size measures.

References

Wan, X., Wang, W., Liu, J. et al. Estimating the sample mean and standard deviation from the sample size, median, range and/or interquartile range. BMC Med Res Methodol 14, 135 (2014). https://doi.org/10.1186/1471-2288-14-135

Examples

es_from_med_quarts(
  q1_exp = 1335, med_exp = 1400,
  q3_exp = 1765, n_exp = 40,
  q1_nexp = 1481, med_nexp = 1625,
  q3_nexp = 1800, n_nexp = 40
)