4. …and some statistics
• There are different kinds of variables:
Categorical or nominal (e.g., colors)
Ordinal (e.g., rate 1 to 10 your happiness)
Interval. The difference between values can be
measured, and is the same (lineal intervals)
Ratio. Same as before, but also 0 means 0. E.g.,
temperature measured in C, 0 does not mean the
absence of temperature.
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5. …and some statistics
• What can we do ?
Nominal
Ordinal Interval
Ratio
Frequency
Yes
Yes
Yes
Yes
Median
No
Yes
Yes
Yes
Add, mean, std. deviation
No
No
Yes
Yes
Ratio, coef. of variation
No
No
No
Yes
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6. References
• Jamieson, S (2004). "Likert Scales: How to
(Ab)use Them" Medical Education,
Vol. 38(12), pp.1217-1218
• de Winter, J. C. F.; Dodou, D. (2010). "Fivepoint Likert items: t test
versus Mann-Whitney-Wilcoxon", Practical
Assessment, Research & Evaluation,
Vol. 15(11).
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