The power of a paired t-test with a covariate

Citation

Hedberg, E. C. & Ayers, Stephanie (2014). The power of a paired t-test with a covariate. Social Science Research. (0) , PMCID: PMC4297322

Abstract

Many researchers employ the paired t-test to evaluate the mean difference between matched data points. Unfortunately, in many cases this test in inefficient. This paper reviews how to increase the precision of this test through using the mean centered independent variable x, which is familiar to researchers that use analysis of covariance (ANCOVA). We add to the literature by demonstrating how to employ these gains in efficiency as a factor for use in finding the statistical power of the test. The key parameters for this factor are the correlation between the two measures and the variance ratio of the dependent measure on the predictor. The paper then demonstrates how to compute the gains in efficiency a priori to amend the power computations for the traditional paired t -test. We include an example analysis from a recent intervention, Families Preparing the New Generation (Familias Preparando la Nueva Generación). Finally, we conclude with an analysis of extant data to derive reasonable parameter values.

URL

http://www.sciencedirect.com/science/article/pii/S0049089X14002282

Keyword(s)

Statistical Power

Reference Type

Journal Article

Journal Title

Social Science Research

Author(s)

Hedberg, E. C.
Ayers, Stephanie

Year Published

2014

DOI

10.1016/j.ssresearch.2014.12.004

PMCID

PMC4297322

NIHMSID

NIHMS650722

Reference ID

5369