Friday, 26 June 2009

Quantitative is qualitative, too...

Yesterday I read an advertisement for a body lotion scientifically proven* to better the skin of 80% of lotion users. The *footnote explained that, in a trial bringing together twenty women, 80% stated the lotion made their skin feel smoother. Does that sound scientific enough? In any case, it illustrates how you turn qualitative judgements (respondents' reported feelings) into "hard" figures, a procedure which as such is not "manipulative" but established scientific practice.

As a matter of fact, qualitative judgements are at the roots of all quantitative measurement, even in natural sciences: you need to decide what exactly you want to measure and determine how to establish a scale before you can start counting. When Swedish astronomer Anders Celsius developed his temperature scale (1742), he based it on the qualitative observation that water evaporated when heated and solidified when cooled. Then he established a scale which put the boiling point at 0 and the freezing point at 100 (no typing mistake - the original Celsius scale is the reverse of what you find on today's thermometers). He decided that the intervals on the scale would be equal. There could have been other solutions: for example, the Richter magnitude scale, used to measure seismic energy released in earthquakes, is logarithmic: point 5 on the Richter scale comes with a shaking magnitude that is ten times stronger than at point 4.

Qualitative analysis establishes concepts, categories and instruments for measuring. Only after all this qualitative work is done, you can take your quantitative measurement: you look at the thermometer and you read 28°C. If you're a big fan of quantitative indicators, enjoy this moment, because it is brief, as the analysis that follows will be qualitative: is 28°C hot, warm, mild, cool or a bit chilly?

No comments: