A cardiologist found a highly significant correlation coefficient (r=0.90, p=0.01) between systolic blood pressure values and serum cholesterol values of patients attending his clinic. Which of the following statement is a wrong interpretation of the correlation coefficient observed? (AIIMS Nov 2012)
|A||Since there is a high correlation, the magnit-udes of both the measurements are likely to close to each other|
|B||A patient with high level of systolic BP is also likely to have a high level of serum cholesterol|
|C||A patient with low level of systolic BP is also likely to have a low level of serum cholesterol|
|D||About 80% of the variation in systolic BP among his patients can be explained by their serum cholesterol values and vice versa.|
Since there is high positive correlation between BP and serum cholesterol, it simply means that BP and serum cholesterol are strongly associated with each other and if the value of serum cholesterol rises the BP will also increase.
High correlation coefficient does not mean that the values of the two variables would be close to each other or if the value of one variable will be high the other variable would also have a high value or vice versa.
- Option d is a correct statement and is in fact describing another type of coefficient known as the Coefficient of Determination. Squaring the correlation coefficient (r2) gives us the coefficient of determination. It tells us the percentage of variability in one variable, which can be accounted for by the other variable.