  This paper is especially written for students and demonstrates the correct
use of nominal and ordinal scaled variables in regression analysis by means of
so-called dummy variables. We start out with examples of body mass index (BMI)
differences between males and females, and between low, middle, and high
educated people. We extend our examples with several explanatory (dummy)
variables and the interactions between dummy variables. Readers learn how to
use dummy variables and their interactions and how to interpret the statistical
results. We included data, SPSS syntax, and additional information on a website
(http://www.ru.nl/sociology/mt/bmi/downloads/) that goes with this text. No
mathematical knowledge is required.
