es_from_med_quarts function

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

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.

Returns

This function estimates and converts between several effect size measures.

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):

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.

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
)

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