es_from_ancova_means_se function

Convert means and standard errors of two independent groups obtained from an ANCOVA model into several effect size measures

es_from_ancova_means_se(
  n_exp,
  n_nexp,
  ancova_mean_exp,
  ancova_mean_nexp,
  ancova_mean_se_exp,
  ancova_mean_se_nexp,
  cov_outcome_r,
  n_cov_ancova,
  smd_to_cor = "viechtbauer",
  reverse_ancova_means
)

Arguments

• n_exp: number of participants in the experimental/exposed group.
• n_nexp: number of participants in the non-experimental/non-exposed group.
• ancova_mean_exp: adjusted mean of participants in the experimental/exposed group.
• ancova_mean_nexp: adjusted mean of participants in the non-experimental/non-exposed group.
• ancova_mean_se_exp: adjusted standard error of participants in the experimental/exposed group.
• ancova_mean_se_nexp: adjusted standard error of participants in the non-experimental/non-exposed group.
• cov_outcome_r: correlation between the outcome and covariate(s) (multiple correlation when multiple covariates are included in the ANCOVA model).
• n_cov_ancova: number of covariates in the ANCOVA model.
• smd_to_cor: formula used to convert the adjusted cohen_d value into a coefficient correlation (see details).
• reverse_ancova_means: a logical value indicating whether the direction of the generated effect sizes should be flipped.

Returns

This function estimates and converts between several effect size measures.

natural effect size measure	MD + D + G
converted effect size measure	OR + R + Z
required input data	See 'Section 19. Adjusted: Means and dispersion'
	https://metaconvert.org/input.html

Details

This function converts the adjusted means standard errors of two independent groups into standard deviations, and then relies on the calculations of the es_from_ancova_means_sd function.

To convert the standard errors into standard deviations , the following formula is used.

$$ancova\_mean\_sd\_exp = ancova\_mean\_se\_exp * \sqrt{n\_exp}$$ $$ancova\_mean\_sd\_nexp = ancova\_mean\_se\_nexp * \sqrt{n\_nexp}$$

Calculations of the es_from_ancova_means_sd() are then applied.

Examples

es_from_ancova_means_se(
  n_exp = 55, n_nexp = 55,
  ancova_mean_exp = 2.3, ancova_mean_se_exp = 1.2,
  ancova_mean_nexp = 1.9, ancova_mean_se_nexp = 0.9,
  cov_outcome_r = 0.2, n_cov_ancova = 3
)

References

Higgins JPT, Li T, Deeks JJ (editors). Chapter 6: Choosing effect size measures and computing estimates of effect. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.3 (updated February 2022). Cochrane, 2022. Available from www.training.cochrane.org/handbook.