Ken Salzwedel

## KNOWING YOUR SCALES OF MEASUREMENT

It is important to know your scales because most statistics have
specific scale requirements. For example, ordinal data (ranks or ratings) can
not be used to find the mean, standard deviation, or variance. The same is
true for nominal data (frequencies). Most of the standard statistical
procedures require at least **INTERVAL SCALE**. Many errors have been made
by authors who have not remembered their scales. This results in incorrect
data analysis and the interpretation of this information is questionable.

To help you remember your scales, use the following acronym:

**NOIR** = **N**o **O**ne** I**s **R**eady, which represents **N**ominal,** O**rdinal,** I**nterval, and **R**atio
scales.

The most important thing you can do when you have a set of data in front of
you is to evaluate the scale you have. Know the characteristics these 4
different scales. If you fail to do this, you may make an analysis error which
invalidates your findings or outcome data. It is always tempting to use, for
example, ANOVA when the data are ordinal scale because this statistic is more
powerful than nonparametric methods such as the Kruskal-Wallis or Friedman
procedures. Remember no one is ready!

Ken Salzwedel

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