korreationskoefficient

The correlation coefficient is a statistical measure that quantifies the strength and direction of a linear relationship between two quantitative variables. It is represented by the Greek letter rho ($\rho$) for a population or 'r' for a sample. The value of the correlation coefficient ranges from -1 to +1.

A correlation coefficient of +1 indicates a perfect positive linear relationship, meaning that as one variable increases, the other variable increases proportionally. Conversely, a correlation coefficient of -1 indicates a perfect negative linear relationship, where as one variable increases, the other variable decreases proportionally. A correlation coefficient of 0 suggests no linear relationship between the two variables. Values between 0 and 1 (or 0 and -1) indicate varying degrees of positive (or negative) linear correlation.

The most common type of correlation coefficient is Pearson's correlation coefficient, which measures the linear association between two continuous variables. Other types, such as Spearman's rank correlation coefficient, are used for ordinal data or when the relationship is not strictly linear.

It is important to note that correlation does not imply causation. A strong correlation between two variables does not necessarily mean that one variable causes the other; there might be a third, unobserved variable influencing both. Therefore, correlation coefficients should be interpreted cautiously, and further analysis is often needed to establish causal relationships.