A study was conducted to assess the relationship between serum HDL2 level (a subfraction of HDL) and carotid intima-media thickness as a marker of atherosclerosis. Interpretation of the results revealed a linear relationship between these 2 variables, with a correlation coefficient r = -0.25 (p = 0.005). Which of the following statements about the results of the study is the most correct?

Question

A study was conducted to assess the relationship between serum HDL2 level (a subfraction of HDL) and carotid intima-media thickness as a marker of atherosclerosis.  Interpretation of the results revealed a linear relationship between these 2 variables, with a correlation coefficient r = -0.25 (p = 0.005).  Which of the following statements about the results of the study is the most correct?

Quizplus · Accepted Answer

11ec25c8_d31d_e019_bc81_3d3eaf04d140_MD0003_00 The correlation coefficient (r) assesses a linear relationship between 2 variables. The null value for the correlation coefficient is 0 (no association), and the sign of the correlation coefficient indicates a positive or negative association. The closer r is to its margins (-1 or 1), the stronger the association. In this study, as there was a negative correlation between HDL2 and carotid intima-media thickness (given r = -0.25 <0), when there was an increase in one of the variables (eg, HDL2), there was a decrease in the other variable (eg, carotid intima-media thickness). This statement regarding the direction of change does not imply causality (Choice B). (Choice C) The association was statistically significant because p <0.05. (Choice D) The strength of the association was weak because 0.25 is close to 0 (in general r >0.5 or r <-0.5 suggests a strong association, although the exact cutoff depends on what is being studied). (Choice E) A positive correlation (r >0) would have meant that increases in HDL2 were associated with increases in carotid-intima thickness. Educational objective: The correlation coefficient (r) shows the strength and direction (positive, negative) of linear association between 2 variables. It does not necessarily imply causality.

A Study Was Conducted to Assess the Relationship Between Serum