Understanding Statistical Noise in Research: 1. Basic Concepts.

The signal is the outcome of interest in a study; it may be the value of a variable or it may be the value of a relationship between variables. Signals in research are distorted by statistical noise. This statistical noise is generated by extraneous variables that may be adequately measured, inadequately measured, unmeasured, or unknown; the subject-to-subject variation in the signal resulting from the effects of these extraneous variables is captured by the standard deviation. Thus, the standard deviation is a measure of statistical noise. This article, the first in a series, explains all of these concepts with the help of examples.