Level of Measurement and Examples Variable X Variable Y Type of correlation Correlation being computed Nominal (voting preference, such as Republican or Democrat) Nominal (gender, such as male or female) Phi coefficient The correlation between voting preference and gender Nominal (social class, such as high, medium, or low) Ordinal (rank in high school graduating class) Rank biserial coefficient The correlation between social class and rank in high school Nominal (family configuration, such as intact or single parent) Interval (grade point average) Point biserial The correlation between family configuration and grade point average Ordinal (height converted to rank) Ordinal (weight converted to rank) Spearman rank correlation coefficient The correlation between height and weight Interval (number of problems solved) Interval (age in years) Pearson productmoment correlation coefficient The correlation between number of problems solved and the age in years