On the Evaluation of Percentage Change: Control Versus Treatment Groups

Abstract

Experimenters faced with the task of evaluating the effect of a treatment frequently must determine the significance of the percentage change observed for a treatment mean relative to the mean of a control. A common error is to treat the mean of control data as a constant rather than a random variable. This error is explored, and a procedure for properly handling such a comparison is presented.

• ANOVA
• Control Group
• Standard Error of Ratio
• Percentage Change
• Drug Treatment

Additional information

Notes on contributors

Robert A. McLean

Dr. McLean is Associate Professor of Statistics at the University of Tennessee in Knoxville, Tennessee. Dr. Welch is Chief of Psychophysiology and Environmental Neurobiology Research at Maryland State Psychiatric Research Center in Baltimore, Maryland.