Chapter7 Flashcards
Biserial correlation
a standardized measure of the strength of relationship between two variables when one of the two variables is dichotomous. The biserial correlation coefficient is used when one variable is a continuous dichotomy (e.g., has an underlying continuum between the categories).
Bivariate correlation
a correlation between two variables.
Coefficient of determination
the proportion of variance in one variable explained by a second variable. It is Pearson’s correlation coefficient squared.
Covariance
a measure of the ‘average’ relationship between two variables. It is the average cross-product deviation (i.e., the cross-product divided by one less than the number of observations).
Cross-product deviations
a measure of the ‘total’ relationship between two variables. It is the deviation of one variable from its mean multiplied by the other variable’s deviation from its mean.
Kendall’s tau
a non-parametric correlation coefficient similar to Spearman’s correlation coefficient, but should be used in preference for a small data set with a large number of tied ranks.
Partial correlation
a measure of the relationship between two variables while ‘controlling’ the effect of one or more additional variables on both.
Pearson’s correlation coefficient
Pearson’s product-moment correlation coefficient, to give it its full name, is a standardized measure of the strength of relationship between two variables. It can take any value from ‚àí1 (as one variable changes, the other changes in the opposite direction by the same amount), through 0 (as one variable changes the other doesn’t change at all), to +1 (as one variable changes, the other changes in the same direction by the same amount).
Point-biserial correlation
a standardized measure of the strength of relationship between two variables when one of the two variables is dichotomous. The point-biserial correlation coefficient is used when the dichotomy is a discrete, or true, dichotomy (i.e., one for which there is no underlying continuum between the categories). An example of this is pregnancy: you can be either pregnant or not, there is no in between.
Semi-partial correlation
a measure of the relationship between two variables while ‘controlling’ the effect that one or more additional variables has on one of those variables. If we call our variables x and y, it gives us a measure of the variance in y that x alone shares.
Spearman’s correlation coefficient
a standardized measure of the strength of relationship between two variables that does not rely on the assumptions of a parametric test. It is Pearson’s correlation coefficient performed on data that have been converted into ranked scores.
Standardization
the process of converting a variable into a standard unit of measurement. The unit of measurement typically used is standard deviation units (see also z-scores). Standardization allows us to compare data when different units of measurement have been used (we could compare weight measured in kilograms to height measured in inches).
