Book Definition: Specific descriptions of concepts involving the conditions of a scientific study. Operational definitions are stated in terms of how the concepts are to be measured or what operations are being employed to produce them.

In Your Own Words

  • Giving definitions of terms used in the hypothesis to give an exact procedure and how you are going to determine your data.
  • Establish measurements and eliminate error.
  • Specifics in an experiment to reduce confounding variables
  • Defining key terms and phrases in the way you want them to be used in your experiment.
  • Narrowing down the possibility of an error by specifically defining nouns and verbs in the hypothesis.
  • To state the procedures with details for the results and experiment.
  • An operational definition defines something (e.g. a variable, term, or object) in terms of the specific process or set of validation tests used to determine its presence and quantity
  • A precise explanation of what's being measured.


  • A student may be testing the effect of exercise on different weight groups. Exercise could be defined as running around the high school track for a hour each day.
  • In an experiment, don't say the subject will drink water each day. The experimenter must define how often each day the subject will drink water and how much water he or she will drink in order to make the experiment more specific.
  • If a student is testing the effect of studying on test performance, then the student would have to define the amount of time and effort used to study.
  • If a student is testing how driving while tired will affect their driving performance, they must define how much driving time accounts for "driving" and what "tired" means in this context (lack of sleep/energy? How will one determine how tired they are?).
  • Operationally defining violence in a video game by measuring the rating of the video game (We want "M" for Mature)
  • If a student is testing the effect of drinking coffee on a person's energy level, he/she needs to define how much coffee they drink daily, when they drink it, etc.
    • video games - mature rating with violence.
    • person - 13-year-old males.
    • plays - one hour everyday for a year at home
  • You cant say you are going to test coffee on four year olds. (no, not because its unethical) You must describe what type of coffee, at what time they will drink the coffee, how long, and what gender. All aspects of the experiment must be explained in great detail
  • If you are going to test the effect of breakfast in the morning, the operational definition would be defining breakfast... cereal, oatmeal, granola bar, etc.
  • A student can test the effect of fast food on differnet athletes and fast food could be define as Burgerking fries
  • Testing the effect of air fresheners in a room, air fresheners could be defined as Febreze, air wick, etc.
  • If you were testing the memory of different age groups, then you must describe the ages and what tests you are making them take
  • If I were measuring sunlights effect on happiness then my operational definition would be the amount of minutes someone would get of sunlight each day.
  • If you were testing broken bones amongst nine year olds the opperational definition would be which bone... arm, wrist, leg...