Variables: variable an event, situation, behavior, or individual characteristic that varies (ie. word length, gender, age), each of these variables represents a general class within which specific instances will vary. The specific instances of these is called the levels or values of the variables. A variable must have two or more levels or values. Some variables will have numeric values hence they will be quantitative (ie. age, your iq). Algebra can be applied to such variables (ie. mesure the mean). Some variables are not numeric and instead identify categories hence they are categorical (ie. gender, occupation). When researchers study stress, they might focus on a number of stressors noise, crowding, school, etc. a researcher would probably choose one stressor to study then develop an operational definition of that type of stressor. They would then carry out research both pertaining to that specific stress www. notesolution. com and the more general concept of stress).