Notice: On March 31, it was **announced** that Statalist is moving from an email list to a **forum**. The old list will shut down on April 23, and its replacement, **statalist.org** is already up and running.

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

From |
Clive Nicholas <clivelists@googlemail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: Interaction of dummy variable with log-transformed variable |

Date |
Fri, 27 Aug 2010 08:25:00 +0100 |

Susan 'P K' wrote: > I have trouble interpreting the following results and would appreciate your > help: > > I ran an OLS regression with an interaction between a dummy variable and a > log-transformed variable on a continuous dependent variable. > > i.e., > > DV = a + b*log-transformed IV + c*log-transformed variable*dummy variable > > The coefficient of the interaction term on the dependent variable (DV) is 42.00, > the coefficient for the log-transformed variable is -6.00. > > What is the the combined weighting factor on the DV? > - Interpretation of the log-transformed variable´s coefficient: One percent > increase in log-transformed variable increases DV by (-6/100) units. > - How can I interpret the coefficient of the interaction term of the > log-transformed variable and the dummy? Several points: (1) You need to add the dummy variable in your model in order to obtain a finer estimate of your interaction term, so that you have Y = a + b_IV + c_D + d_IV*D + e (2) Once done, the easiest interpretation of _d_ is that the effect of your logged IV on Y turns negative when the dummy shifts to 1. If _d_ attains significance, it means that the effect of your logged IV on Y varies by the values of your dummy variable; (3) You don't mention if Y is also logged. If it is, you might be better served fitting this model using -glm-. -- Clive Nicholas [Please DO NOT mail me personally here, but at <clivenicholas@hotmail.com>. Please respond to contributions I make in a list thread here. Thanks!] "My colleagues in the social sciences talk a great deal about methodology. I prefer to call it style." -- Freeman J. Dyson. * * 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/

**Follow-Ups**:**AW: st: Interaction of dummy variable with log-transformed variable***From:*P K <statistics_2009@yahoo.de>

**References**:**st: Interaction of dummy variable with log-transformed variable***From:*P K <statistics_2009@yahoo.de>

- Prev by Date:
**Re: st: interpretation of squared term** - Next by Date:
**Re: st: interpretation of squared term** - Previous by thread:
**st: Interaction of dummy variable with log-transformed variable** - Next by thread:
**AW: st: Interaction of dummy variable with log-transformed variable** - Index(es):