In this case, the dimension of time flows from left to right, suggesting that if there is any correlation between the blue events and the red events, blue must cause red. A straight rho (product-moment) correlation gives an r of -.356 but when covariance in effect shifts the blue bars to the right there is such a high correlation that even a jaded statistician would concede causality. Readers will find Bradley E. Huitema's (professor of psychology at Western Michigan University) book Analysis of Covariance and Alternatives (Wiley, New York, 1980) instructive. ISBN: 0471420441 : 9780471420446 - Professor Huitema told us a new edition was coming in January 2009. Made it in October 2011. $125 in hardcover; $80 on Nook. |
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