Source: Image of Measuring Tape, Public Domain: http://morguefile.com/archive/display/106141
Actually measuring the data the you set out to capture.
Consistency in the valuation of a variable.
The process of determining the value of a variable.
The "effect" or the outcome of the change in the independent variable.
The "cause" driving the change in the dependent variable.
A characteristic such as age, class, income, education, ect.. that varies throughout the population as a whole.
A simplified, working representation of the social world; i.e. "class" or "family."