Superpower (version 0.2.4)

ANCOVA_analytic: Power Calculations for Factorial ANCOVAs

Description

Complete power analyses for ANCOVA omnibus tests and contrasts. This function does not support within subjects factors.

Usage

ANCOVA_analytic(
  design,
  mu,
  n = NULL,
  sd,
  r2 = NULL,
  n_cov,
  alpha_level = Superpower_options("alpha_level"),
  beta_level = NULL,
  cmats = list(),
  label_list = NULL,
  design_result = NULL,
  round_up = TRUE
)

Value

One, or two, data frames containing the power analysis results from the power analysis for the omnibus ANCOVA (main_results) or contrast tests (contrast_results). In addition, every F-test (aov_list and con_list) is included in a list of power.htest results. Lastly, a (design_param) list containing the design parameters is also included in the results.

Arguments

design

Output from the ANOVA_design function

mu

Vector specifying mean for each condition

n

Sample size in each condition

sd

Standard deviation for all conditions (or a vector specifying the sd for each condition)

r2

Coefficient of Determination of the model with only the covariates

n_cov

Number of covariates

alpha_level

Alpha level used to determine statistical significance

beta_level

Type II error probability (power/100-1)

cmats

List of matrices for specific contrasts of interest

label_list

An optional list to specify the factor names and condition (recommended, if not used factors and levels are indicated by letters and numbers).

design_result

Output from the ANOVA_design function

round_up

Logical indicator (default = TRUE) for whether to round up sample size calculations to nearest whole number

References

Shieh, G. (2020). Power analysis and sample size planning in ANCOVA designs. Psychometrika, 85(1), 101-120.

Examples

# Simple 2x3 ANCOVA

ANCOVA_analytic(
design = "2b*3b",
mu = c(400, 450, 500,
      400, 500, 600),
n_cov = 3,
sd = 100,
r2 = .25,
alpha_level = .05,
beta_level = .2,
round_up = TRUE
)