TSLS.size: Sample Size Calculator for the Power of Asymptotic T-test

In ivmodel: Statistical Inference and Sensitivity Analysis for Instrumental Variables Model

Sample Size Calculator for the Power of Asymptotic T-test

Description

TSLS.size computes the minimum sample size required for achieving certain power of asymptotic t-test of TSLS estimator.

Usage

TSLS.size(power, beta, rho_ZD, sigmau, sigmaDsq, alpha = 0.05)

Arguments

power	The desired power over a constant.
beta	True causal effect minus null hypothesis causal effect.
rho_ZD	Correlation between the IV Z and the exposure D.
sigmau	Standard deviation of potential outcome under control. (structural error for y)
sigmaDsq	The variance of the exposure D.
alpha	Significance level.

Details

The calculation is based on inverting the power formula given in Freeman (2013).

Value

Minimum sample size required for achieving certain power of asymptotic t-test of TSLS estimator.

Author(s)

Yang Jiang, Hyunseung Kang, and Dylan Small

References

Freeman G, Cowling BJ, Schooling CM (2013). Power and Sample Size Calculations for Mendelian Randomization Studies Using One Genetic Instrument. International journal of epidemiology, 42(4), 1157-1163.

See Also

See also ivmodel for details on the instrumental variables model.

Examples

# Assume we performed an asymptotic t-test of TSLS estimator in a study 
# with one IV (l=1) and the only one exogenous variable is the intercept 
# (k=1). We want to calculate the minimum sample size needed for this 
# test to have an at least 0.8 power.

# Suppose the null hypothesis causal effect is 0 and the true causal 
# effect is 1 (beta=1-0=1).
# The correlation between the IV and exposure is .5 (rho_ZD= .5).
# The standard deviation of potential outcome is 1(sigmau= 1). 
# The variance of the exposure is 1 (sigmaDsq=1).
# The significance level for the study is alpha = .05.

### minimum sample size required for aysmptotic t-test
TSLS.size(power=.8, beta=1, rho_ZD=.5, sigmau=1, sigmaDsq=1, alpha =.05)

ivmodel documentation built on April 9, 2023, 5:08 p.m.