What is a correlation coefficient?
It is a statistic widely used in psychological research, including test design. It shows the degree of relationship between two measures. It can range from – 1.00 to + 1.00. If high scores on one trait (e.g. intelligence) are associated with high scores on the other measure (e.g. school grades), then the correlation is positive, e.g. .52. If high scores on one measure are associated with low scores on the other, then it is negative, e.g. -.68 between a measure of warmongering disposition and intelligence. When correlations are so high that they are very unlikely to have occurred by chance alone, then researchers can be confident that the two traits are significantly related to each other and advise persons to make decisions based on the test scores for those traits. If correlations are based on very large samples of persons, e.g. 100 or more, then correlations even as low as .20 can be significant (not due to chance) and provide valuable information.
