The point-biserial correlation coefficient rpbi is a measure to estimate the degree of relationship between a naturally dichotomous nominal variable and an interval or ratio variable. For example, a researcher might want to examine the degree of relationship between gender (a naturally occurring dichotomous nominal scale) and the students’ performance in the final examination testing persuasion skills and knowledge as measured by scores (0–100 points; a ratio scale). Certainly, a variety of different correlation coefficients (such as Pearson correlation coefficient, phi correlation coefficient, Spearman’s rho, partial correlation, and part correlation) have been developed over the years for measuring relationships between sets of data. Actually, the point-biserial correlation is one of the most commonly used statistics in educational assessment. This entry provides an overview ...
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