Читать книгу Methods in Psychological Research - Annabel Ness Evans - Страница 95

Sometimes we would like to measure the relationship between two variables when a third has an influence on them both. We can partial out the effects of that third variable by computing a partial correlation. Suppose there is a correlation between age and income. It seems reasonable that older people might make more money than younger people. Is there another variable that you think might be related to age and income? How about years of education? Older people are more likely to be better educated, having had more years to go to school, and it seems likely that better-educated people earn more. So what is the true relationship between age and income if the variable years of education is taken out of the equation? One solution would be to group people by years of education and then conduct a number of separate correlations between age and income for each education group. Partial correlation, however, provides a better solution by telling us what the true relationship is between age and income when years of education has been partialled out.