epts (version 1.2.1)

srtDataSimulation: Simulate Simple Randomized Trial (SRT) Data

Description

This function simulates a Simple Randomized Trial (SRT), with multiple intervention arms, pre-test and post-test scores, and individual-level attrition. No clustering or hierarchical structure is assumed.

Usage

srtDataSimulation(ni, tpi, np, sigma, B0, es, seed, attritionrates, covariates)

Value

A data.frame containing:

ID

Participant ID

interventions

Intervention assignment (0 = control, 1 to ni = intervention groups)

covariates

Simulated covariates

posttest

Posttest score (NA if participant attrited)

Arguments

ni

The number of intervention groups excluding the control group.

tpi

The proportions (in percent) assigned to each group, with the first value for the control group followed by the intervention groups. Must sum to 100. It should be specified as a numeric vector of length ni + 1.

np

The total number of participants.

sigma

The standard deviation of individual-level error for the post-test score.

B0

The intercept term in the model.

es

The standardized effect sizes for each intervention group. It should be specified as a numeric vector.

seed

The random seed for reproducibility.

attritionrates

The attrition rates for each group, including the control group. It should be specified as a numeric vector of length ni + 1.

covariates

List of covariate specifications. Each element should be a list with the following fields:

name

Character. Name of the covariate.

type

Character. Either "continuous" or "categorical".

sd

Numeric. Standard deviation (only for continuous covariates).

coefficient

Numeric. Coefficient (only for continuous covariates).

levels

Character vector. Category levels (only for categorical covariates).

probs

Numeric vector. Sampling probabilities (must sum to 1) (categorical only).

reference

Character. Reference category (categorical only).

coefficients

Named list of numeric values. Coefficients for each non-reference level.

Examples

covariates <- list(
 list(name = "pretest", type = "continuous", sd = 1, coefficient = 1.7),
 list(name = "gender", type = "categorical", levels = c("Male", "Female"),
 probs = c(0.3, 0.7), reference = "Male", coefficients = list(B = -0.5)),
 list(name = "ethnicity", type = "categorical", levels = c("White", "Black", "Asian"),
 probs = c(0.3, 0.3, 0.4), reference = "White", coefficients = list(B = 1.02, C = 1.3))
)

srtdata <- srtDataSimulation(ni = 3, np = 1000, tpi = c(30, 30, 20, 20),
sigma = 1, B0 = 1.45,  es = c(0.2, 0.3, 0.1), seed = 1234,
attritionrates = c(0.1, 0.1, 0.1, 0), covariates = covariates) 
head(srtdata)