Inconsistent Beta Coefficient Sign Between Multiple and Simple Regression

Posted by Joe on Nov 27, 2011; 10:57am
URL: http://spssx-discussion.165.s1.nabble.com/Inconsistent-Beta-Coefficient-Sign-Between-Multiple-and-Simple-Regression-tp5026243.html

I am conducting a multiple Linear regression with 3 predictors, all variables are continuous and N=51.  Before doing linear regression analysis, I did first a simple linear regression and found that all the predictors have positive correlation with the outcome variable.
Surprisingly, when I did the multiple linear regression, one of the predictors have negative B unstandardized coefficients, with less than -1.0 coefficient, VIF value less than 10, and these are no indication of multicollinearity problem.

Is there anything wrong with the result? Please kindly give any advice how to explain this case.

Thank you.
Joe