Contents
Do we overestimate the within variability The impact of measurement error on intraclass coefficient estimation?
Theorem 1 highlights that the within-variance estimator applied to a variable, contaminated by measurement error yields biased estimates. Eq. 11 proves that applying the standard estimator of the within-variance to a variable, contaminated by measurement error overestimates the within-variance.
What can distort a correlation?
The authors describe and illustrate 6 factors that affect the size of a Pearson correlation: (a) the amount of variability in the data, (b) differences in the shapes of the 2 distributions, (c) lack of linearity, (d) the presence of 1 or more “outliers,” (e) characteristics of the sample, and (f) measurement error.
How is correlation measured?
The correlation coefficient is measured on a scale that varies from + 1 through 0 to – 1. Complete correlation between two variables is expressed by either + 1 or -1. When one variable increases as the other increases the correlation is positive; when one decreases as the other increases it is negative.
When does measurement error inflate the correlation coefficient?
If we select subjects to give a wide range of the measurement, the natural approach when investigating measurement error, this will inflate the correlation coefficient. The correlation coefficient between repeated measurements is often called the reliability of the measurement method.
How to re-analyze intraclass correlation ( ICC ) theory?
A re-analysis of intraclass correlation (ICC) theory is presented together with Monte Carlo simulations of ICC probability distributions. A partly revised and simplified theory of the single-score ICC is obtained, together with an alternative and simple recipe for its use in reliability studies.
What is the value of the intra class correlation coefficient?
1. Introduction The intra-class correlation coefficient (ICC) is a number, usually found to have a value between 0 and 1. It is a well-known statistical tool, applied for example in medical, psychological, biological and genetic research.
How is the ICC of an intraclass calculated?
Very generally speaking, the ICC is calculated as a ratio ICC = (variance of interest) / (total variance) = (variance of interest) / (variance of interest + unwanted variance).