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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.


VariableVariable:  Any aspect or characteristic that varies from case to case or over different times of observation.



 



Ordinal                                    



Ratio                                       

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




  1. “How many credit cards do you have?”_______6_________________6__________



_______ME______   ______RANK____   ___INTERVAL___   __RATIO_____  = __RATIO_


  1. “On average, how many packages of cigarettes do you smoke each day?” _____2_________2____


____ME____  


_____RANK__  

____ME_______INTERVAL____   _____RANK__   ___INTERVAL____   ___RATIO_______RATIO____  = ____ RATIO ___


  1. “What languages do you speak at home?” __Cantonese,__Cantonese, Swahili, Flemish, Congolese _



__ME___ME_   ____   ____NO________NO____   ___NO______NO___    ___NO______NO___    = ____NOMINAL________NOMINAL____


  1. “Are you over 20 years old?” __ YES ____


___ME____  


___RANK____  

___ME_______NO ___RANK____SCALE___   ___NO__NO SCALE___   __NO RATIO____RATIO____  = ___ORDINAL______ORDINAL___


 

  1. “What were the traffic conditions yesterday afternoon?” ___FLUID,___FLUID, SLOW, STOPPAGE__STOPPAGE__


____ME_____  


__RANK___  

____ME_______NO __RANK___SCALE___   __NO__NO SCALE___   __NO RATIO____RATIO____   = ___ORDINAL_______ORDINAL____


  1. “What percentage of the population earns less than $5,000 annually?” ____20____20 percent_______percent_______


__ME__  


__ME__   ___RANK_____RANK__   ____ SCALE ___   ___RATIO_____RATIO__   = ___RATIO______RATIO___


  1. “What is your gender?” (Trichotomy) ___ MALE, FEMALE, OTHER ____


__ME______  


_____ME______   ___NONO RANK ___   __NO__NO SCALE___SCALE___   ___NO___NO RATIO___RATIO___   = ____NOMINAL________NOMINAL____

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