Changes

==Correlation coefficients==

==Correlation coefficients==

Correlation coefficients are used when comparing two [[Quantitative data#Data types|quantitative variables]], and are based upon the '''covariance''' between these variables amongst the individuals in the study population. The covariance can be viewed as how the two variables of interest differ in individuals in relation to their mean values in the whole population, but put more simply, is a measure of how two different variables change in relation ''to each other''. This value is standardised in order to give a correlation coefficient, which lies between -1 (indicating a perfect negative correlation) and +1 (indicating a perfect positive correlation), with a coefficient of 0 indicating no correlation.

Correlation coefficients are used when comparing two [[Data types#Quantitative data|quantitative variables]], and are based upon the '''covariance''' between these variables amongst the individuals in the study population. The covariance can be viewed as how the two variables of interest differ in individuals in relation to their mean values in the whole population, but put more simply, is a measure of how two different variables change in relation ''to each other''. This value is standardised in order to give a correlation coefficient, which lies between -1 (indicating a perfect negative correlation) and +1 (indicating a perfect positive correlation), with a coefficient of 0 indicating no correlation.

==Ratio measures==

==Ratio measures==