A cardiologist found a highly significant correlation coefficient (r = 0.90) between systolic P and serum cholesterol values of the patients attending his clinic. Which of the following statements is a wrong inte retation of the correlation coefficient observed-
Correct Answer: Since there is a high correlation, the magnitude of both the measurements are likely to be close to each other
Description: Correlation coefficients:
– Pearson’s Correlation coefficient:
– Spearman’s Rank Correlation coefficient
Coefficient of determination:
– Is the percentage of variation in a variable that is explained by one or more of the others
– Is generally obtained in a regression setup
– Coefficient of determination = (Correlation coefficient)2 = r2
In the given question, a cardiologist found a highly significant correlation coefficient (r = 0.90, p= 0.01) between the systolic blood pressure values and serum cholesterol values of the patients attending his clinic, Since r = + 0.90 (p = 0.01; implies significant relationship), it means there is a strong positive correlation between systolic blood pressure (SBP) and serum cholesterol (SC); therefore as SBP increases, SC will also increase and vice-versa. Thus, a patient with a high level of systolic BP is also likely to have a high level of serum cholesterol AND a patient with a low level of systolic BP is also likely to have a low level of serum cholesterol.
Since r = + 0.9; Coefficient of determination = r2 = (0.9)2 = 0.81
Interpretation of r2: 0.81 or 81% of variation in systolic blood pressure among patients can be explained by their serum cholesterol values and vice-versa.
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Social & Preventive Medicine
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