Correlation is a mutual relationship or connection between two or more things. In our example a correlation of +0.80 between height and weight for adults means. A) 80%. The correlation measures the extent to which knowing the value of height helps you to predict the value of weight. Even with a high correlation of +0.80, we cannot really expect two persons with exactly the same height to have exactly the same weight. Almost always there is some difference. What this says is that, as height goes higher, the weight goes higher, too.