# Concordance correlation coefficient

Command: | Statistics Agreement & responsiveness Concordance correlation coefficient |

## Description

The concordance correlation coefficient (Lin, 1989) evaluates the degree to which pairs of observations fall on the 45° line through the origin.

## Required input

Select the variables for the two techniques you want to compare.

## Results

The concordance correlation coefficient *ρ*_{c} contains a measurement of precision *ρ* and accuracy *C*_{b}:

where

*ρ*is the Pearson correlation coefficient, which measures how far each observation deviates from the best-fit line, and is a**measure of precision**, and*C*_{b}is a bias correction factor that measures how far the best-fit line deviates from the 45° line through the origin, and is a**measure of accuracy**.

## Descriptive scale

McBride (2005) suggests the following descriptive scale for values of the concordance correlation coefficient (for continuous variables):

Value of ρ_{c} | Strength of agreement |
---|---|

< 0.90 | Poor |

0.90 - 0.95 | Moderate |

0.95 - 0.99 | Substantial |

>0.99 | Almost perfect |

## Literature

- Lin L.I-K (1989) A concordance correlation coefficient to evaluate reproducibility. Biometrics 45:255-268. [Abstract]
- Lin L.I-K (2000) A note on the concordance correlation coefficient. Biometrics 56:324-325.
- McBride GB (2005) A proposal for strength-of-agreement criteria for Lin's Concordance Correlation Coefficient. NIWA Client Report: HAM2005-062. (PDF)

## See also

- Intraclass correlation coefficient

- Inter-rater agreement (kappa)
- Cronbach's alpha
- Accuracy and Precision

## External links

- Concordance correlation coefficient on Wikipedia.