- correlation
**1.**The mutual or reciprocal*relation*of two or more items or parts.**2.**The act of bringing into such a*relation*.**3.**The*degree*to which variables*change*together.-**product-**a statistical*moment*c.*procedure*which yields the c.*coefficient*referred to as*r*(−1.00 to +1.00) and involves the actual values, rather than the ranks (*rank**order*) of the measurements.-**rank-**the*difference*c.*relationship*between paired*series*of measurements, each ranked according to*magnitude*, which yields a*coefficient*known as rho; the*value*of rho varies from*zero*(no*relationship*) to +1.00 (perfect relationship).* * *

__n.__*(in statistics)*the extent to which one of a pair of characteristics affects the other in a series of individuals. Such pairs of observations can be plotted as a series of points on a graph. If all the points on the resulting scatter diagram are in a straight line (which is neither horizontal nor vertical), the correlation coefficient may vary within the range of +1, where an increase of one variable is always associated with the corresponding increase in the other, to -1, where an increase of one variable is associated with a constant decrease of the other; a coefficient of 0 indicates no dependence of the one characteristic on the other of a straight line type. The regression coefficient is the average extent to which a unit increase of one characteristic influences the increase/decrease of the other. Where several factors appear to correlate with the onset of disease the relative importance of each may be calculated by the statistical technique known as multivariate analysis.* * *

cor·re·la·tion (kor″ə-laґshən) the degree to which one phenomenon or random variable is associated with or can be predicted from another. In statistics this usually refers to the degree to which a linear predictive relationship exists between random variables, as measured by a correlation coefficient (q.v.). Correlation is*positive*(never larger than 1) when both variables increase or decrease together;*negative*or*inverse*(never smaller than −1) when one variable increases when the other decreases; and defined as zero when a change in one variable does not affect the other.

*Medical dictionary.
2011.*