Research on psychological disorders includes: presenting problem, causation, treatment and outcome. Internal and external validity: confound relates to internal validity any factor occurring in a study that makes the results uninterprable oex. Help rule out alternative explanations for results aka strengthening internal validity. Half the gamblers were assigned alcohol, other half was not orandomization is the process of assigning people to different research groups in such a way that each person has an equal chance of being place in any group. Eliminates any systematic bias oanalogue models create in the controlled conditions of the lab aspects that are comparable (analogous) to the phenomena under study. Bulimia study - could ask volunteers to binge eat in the lab, quesionoing them before they arte, while they were eating, and after they finished to learn whether eating in this way made them feel more or less anxious.