The Correlation Coefficient

Abstract

Correlation coefficients are used to measure the strength of the relationship or association between two quantitative variables. For example, Table 1 shows height, muscle strength and age in 41 alcoholic men. We will begin with the relationship between height and strength. Figure 1 shows a plot of strength against height. This is a scatter diagram. Each point represents one subject. If we look at Figure 1, it is fairly easier to see that taller men tend to be stronger than shorter men, or, looking at the other way round, that stronger men tend to be taller than weaker men. It is only a tendency, the tallest man is not the strongest not is the shortest man the weakest. Correlation enables us to measure how close this association is.