7 – Measuring Variables
Why should I care?
The accuracy of your project depends on whether or not you are measuring the right phenomenon. The type of measurement determines what kind of tables and calculations you can generate, and also determines how far you can go when you interpret the data.
Variable: Any aspect or characteristic that varies from case to case or over different times of observation.
| Definitions | Example | Instrument |
| Object of Measurement | ||
| Aptitude or Ability | Creativity | Interview |
| Behaviour | Physical Violence | Laboratory |
| Level of knowledge | Do you know about chemistry? | Questionnaire |
| Opinion | Wrong for psychologists to advertise? | Questionnaire |
| Perception, Self-Perception | What Churchill saw in Hitler | Content Analysis |
| Personal characteristic | Eye Colour, Age, Skin Colour, Height | Recording |
| Physical Trace | Kitchen Technology | Artefacts |
| Socio-demographic characteristic | Income | Questionnaire |
| Type of Data | ||
| Qualitative | Objects of quality, not measured by numbers. (Eye colour) | |
| Quantitative | Objects measured in quantities, using numbers. (Income) | |
| Levels of Measurement (pp. 217-218) | ||
| Nominal | Categories. | Music preference? Jazz, Rock, Classical. |
| Ordinal | Ordered Categories. | Music? Jazz 1, Rock 2, Classical 3. |
| Interval | Equal space scale. | From 1 – 10. Jazz 10, Rock 4, Classical 1. |
| Ratio | Scale with absolute zero. | Income scale: 0 – 10 M$ |
Why is it so useful to aim for ratio data?
Exercise
Answer the question as if you were the respondent of a survey. (You don’t have to be honest)
Then, indicate the 4 characteristics of the data, such as:
- mutually exclusive or not
- rank ordering or not
- equal and measured spacing or not
- comparing scores as ratios of each other or not
Finally, state the type of level of measurement = nominal, ordinal, interval or ratio
- “How many credit cards do you have?”_______6__________
_______ME______ ______RANK____ ___INTERVAL___ __RATIO_____ = __RATIO_
- “On average, how many packages of cigarettes do you smoke each day?” _____2____
____ME____ _____RANK__ ___INTERVAL____ ___RATIO____ = ____ RATIO ___
- “What languages do you speak at home?” __Cantonese, Swahili, Flemish, Congolese _
__ME_ ____ ____NO____ ___NO___ ___NO___ = ____NOMINAL____
- “Are you over 20 years old?” __ YES ____
___ME____ ___RANK____ ___NO SCALE___ __NO RATIO____ = ___ORDINAL___
- “What were the traffic conditions yesterday afternoon?” ___FLUID, SLOW, STOPPAGE__
____ME_____ __RANK___ __NO SCALE___ __NO RATIO____ = ___ORDINAL____
- “What percentage of the population earns less than $5,000 annually?” ____20 percent_______
__ME__ ___RANK__ ____ SCALE ___ ___RATIO__ = ___RATIO___
- “What is your gender?” (Trichotomy) ___ MALE, FEMALE, OTHER ____
__ME______ ___NO RANK ___ __NO SCALE___ ___NO RATIO___ = ____NOMINAL____