Interaction (statistics)  From Wikipedia, the free encyclopedia
Jump to: navigation, search  In statistics, an interaction[1][2]
may arise when considering the relationship among three or more
variables, and describes a situation in which the simultaneous
influence of two variables on a third is not additive. Most
commonly, interactions are considered in the context of
regression analyses.  The presence of interactions can have
important implications for the interpretation of statistical
models. If two variables of interest interact, the relationship
between each of the interacting variables and a third "dependent
variable" depends on the value of the other interacting
variable. In practice, this makes it more difficult to predict
the consequences of changing the value of a variable,
particularly if the variables it interacts with are hard to
measure or difficult to control.  The notion of "interaction" is
closely related to that of "moderation" that is common in social
and health science research: the intera