levels of measurement

• Levels of measurement

  Nominal, ordinal and interval are levels of measurement; each is more precise and provides more information than the previous level.
• Nominal data


  Often referred to as categorical data, nominal data refers to named or labelled variables that do not include numerical values. These variables are discrete (they don't overlap), and the categories have no natural order.
• Examples of nominal data

  When using nominal data other than frequency, psychologists can't discuss differences between each category.

  Examples - Gender, hair colour, country of birth, career choice and taste in music.
• Ordinal data


  It has the same properties as nominal data; however, the categories have a natural order. The difference between each point in an ordinal scale is not consistent.
• Examples of ordinal data


  Include positions in a competition (1st, 2nd, 3rd). Choices on a Likert scale (e.g. how happy u feel 1-10) and relative height among a group of people (tall, medium, small).
• Interval data


  A data type which is measured along a scale, in which each point is placed at equal distance from one another.
• Examples of interval data

  Weight in grams, lengths in millimeters, temperature in celsius, and time in seconds.
• Converting between types of data


  It is possible to convert from a higher level of measurement to a lower level of measurement. Interval can be converted into ordinal, and ordinal can be converted into nominal.
• Converting interval to ordinal


  Start with participant interval scores e.g., reaction times or scores (IQ, personality) on a standardised test.

  Each participant is assigned a rank score to turn the interval measure into an ordinal measure. This is done by listing each participant from the highest scoring to the lowest scoring.

  Any participant with the same interval score share the same rank position.
• Converting ordinal to nominal


  To convert data, separate categories are created e.g. fast reaction/slow reaction, intelligent/unintelligent.

  The highest-ranked half of the participants are assigned to one category, and the other half to the other category.