PSYC 2002 Lecture 6: Statistics
4 Feb 2019
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Always, always draw a scatter plot first. Numerator : sum of products of deviations for x and y. Denominator : square root of product is ss values for x and y. Correlation coefficient: excel function correl(array1,array2) array1 is the set of x values array2 is the set of y values. How to interpret size of correlation coefficient. Use r2 to compare correlations; the proportion of the variance r of 0. o does not mean three times more correlation than r of 0. 3 accounted for. For psychopathy example, r = 0. 96; r 2. 92. 5% of the variability in emotion identification was accounted for by a person"s psychopathy score. Linearity r only measures direction and degree of linear relationship (it does not measure non-linear relationships, such as curvilinear relationships) Although correlation may be associated with causation, it does not necessitate causation. Need to examine potential effect of 3rd variables (ex: murder rates & ice-cream sales)
