A
mixed model is a
statistical model containing both
fixed effects and
random effects. These models are useful in a wide variety of disciplines in the physical, biological and social sciences. They are particularly useful in settings where
repeated measurements are made on the same
statistical units (
longitudinal study), or where measurements are made on clusters of related statistical units. Because of their advantage in dealing with missing values, mixed effects models are often preferred over more traditional approaches such as repeated measures
ANOVA.