es_from_ancova_f_pval function

Convert a two-tailed p-value of an ANCOVA t-test into several effect size measures.

es_from_ancova_f_pval(
  ancova_f_pval,
  cov_outcome_r,
  n_cov_ancova,
  n_exp,
  n_nexp,
  smd_to_cor = "viechtbauer",
  reverse_ancova_f_pval
)

Arguments

• ancova_f_pval: a two-tailed p-value of an F-test in an ANCOVA (binary predictor)
• 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.
• n_exp: number of participants in the experimental/exposed group.
• n_nexp: number of participants in the non-experimental/non-exposed group.
• smd_to_cor: formula used to convert the adjusted cohen_d value into a coefficient correlation (see details).
• reverse_ancova_f_pval: 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	D + G
converted effect size measure	OR + R + Z
required input data	See 'Section 18. Adjusted: ANCOVA statistics, eta-squared'
	https://metaconvert.org/input.html

Details

This function converts the p-value of an ANCOVA (binary predictor) into a t value, and then relies on the calculations of the es_from_ancova_t() function.

To convert the p-value into a t-value, the following formula is used (table 12.3 in Cooper):

$$df = n\_exp + n\_nexp + n\_exp - 2 - n\_cov\_ancova$$ $$t = | pt(ancova\_f\_pval/2, df = df) |$$

Then, calculations of the es_from_ancova_t() are applied.

Examples

es_from_ancova_f_pval(
  ancova_f_pval = 0.05, cov_outcome_r = 0.2,
  n_cov_ancova = 3, n_exp = 20, n_nexp = 20
)

References

Cooper, H., Hedges, L.V., & Valentine, J.C. (Eds.). (2019). The handbook of research synthesis and meta-analysis. Russell Sage Foundation.