# st: Multiple dummies - what does the constant measure?

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## st: Multiple dummies - what does the constant measure?

 Suppose you have two sets of categorical dummies: A1 A2 A3 A4 B1 B2 B3 B4 When you regress Y on them you must drop one category from each dummy to avoid the dummy variable trap, i.e., Y = a + A1 + A2 + A3 + B1 + B2 + B3 + e.   So Stata's regression output looks like this: A1     0.826 A2     0.224 A3     0.187 B1     0.376 B2     0.997 B3     0.736 _cons  0.556 Question:  What does the coefficient for the constant represent?  Is it the intercept of A4 plus the intercept for B4?  If so, how does one ascertain the intercepts for A4 and B4 separately? Does one pick different dummies to omit and run the regression again? Thx. Jimmy Verner Graduate Student University of Texas at Dallas Jimmy L. Verner, Jr. Verner & Brumley, P.C. 3131 TurtleCreek Blvd. Penthouse Suite Dallas, Texas  75219 214.526.5234 214.526.0957.fax [hidden email] www.vernerbrumley.com Board Certified, Family Law and Civil Trial Law, Texas Board of Legal Specialization Also admitted in New Mexico * *   For searches and help try: *   http://www.stata.com/help.cgi?search*   http://www.stata.com/support/statalist/faq*   http://www.ats.ucla.edu/stat/stata/