Choosing a statistical test

Question 1

What are levels of measurement?

Answer 1

Quantitative data can be divided into different levels of measurement and this is the third factor influencing the choice statistical test. There are three levels of measurement: nominal, ordinal and interval.

Question 2

What is nominal data?

Answer 2

The level of data used when categorising something. Named categories are established by the researcher and an item is counted when it falls into this category. For example, the number of males and females in a psychology class, or the number of monolingual, bilingual and multilingual students in the school. Each ‘item’ only appears in one category.

Question 3

What is ordinal data?

Answer 3

This is when data is ranked so that it is possible to see the order of scores in relation to one another.

Question 4

What is interval data?

Answer 4

This is a more sophisticated level of data. It not only gives the rank order of scores but it also details the precise intervals between scores. The measurement being used might be temperature or weight, where there is a universally accepted scale of measurement. For example, in the 100m race the finishing times of runners would be interval data: Clarke, N- 11.4 seconds; Smith, H- 11.9 seconds; Lloyd, P- 12.1 seconds.