CAS MA 416 Lecture 3: MA416 Class 3
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Ma416 class 3: the correlation coefficient r (sample correlation), (population) The correlation coefficient measures how closely the points of the scatter plot fall along the regression line (sort of ). It is not a measure of the steepness of the regression line. The correlation coefficient is a standardized measure that is independent of the scale of x or y; the correlation between height and weight is the same whether weight is measured in pounds, ounces, grams, kilograms, etc. Correlation is non-directional, measuring the mutual association between two measurement variables (unlike regression, which is implies a direction to the association with the independent and dependent variable). R close to 0 indicates little or no association. The numerators of the slope and r are the same; r=0 if and only if (cid:2869) =0. Formulas relating the slope from a regression line to the correlation coefficient: rpopulation = 0.