Variability refers to the extent to which scores are spread out in a data set.

Factors that may explain differences in the level or direction of project outcomes from the anticipated outcomes or for different groups.

Psychometric properties refer to the reliability and validity of measurement instruments in a study.

A variable is a property whose value can change. For example, height and weight, money spent, or life satisfaction are all variables. Variables are examined and measured in research during the testing of hypotheses.

A variable not included in a study's design or analysis that may have influenced program results, for example, when important characteristics of experimental and comparison groups do not match.

Factors in the community or region that can affect how a project is implemented, how- and how successfully- it achieves its outcomes and impacts, and which sectors of the target population do and do not benefit. Contextual variables may include economic, political, institutional, environmental, security, and sociopsychological factors and the sociocultural environment.

A dichotomous variable refers to a variable that consists of two categories. Biological sex (male or female) or deployment history (deployed or never deployed) are examples of dichotomous variables.

Confounding occurs when additional factors in a study distort the true relationship between a treatment and its outcome, either resulting in the presentation of a false association or the masking the true association.

Control variables are variables that stay the same throughout an experiment/study. In our case, things like sex or race are common controls. Essentially when you control for a variable you hold or remove the effect of that variable on the outcome/dependent variable.

Dependent variables are those affected by the independent variable(s). In experimental research, the dependent variable measures the effect of the independent variable on the outcome. In nonexperimental research, the dependent variable, although not manipulatable, can be causally inferred to result from the independent variable.

Independent variables are those which researchers believe causes an outcome on another variable, the dependent variable. In experimental research, the independent variable is manipulated by the researcher and applied to the subject or subject group to measure the effect of the independent variable on the dependent variable. In nonexperimental research, the independent variable is the variable which, although not manipulatable, is the variable from which causal inference is implied.