In statistics, correlation is a measure of association between two numeric variables. The strength of correlation between two variables is represented by the correlation coefficient, represented by the abbreviation r. Correlation coefficients range between -1 to 1.
Though the correlation coefficient indicates the strength of an association, it does not provide information about whether the change in one variable is caused by the other.
For example, if the correlation between adult smoking prevalence and child poverty is 0.7—a strong correlation—we cannot say either that adult smoking causes child poverty or, inversely, that child poverty causes smoking. We only know that as one of these variables increases, the other tends to increases.