Why model?

The first question that arises frequently--sometimes innocently and sometimes not--is simply, "Why model?" Imagining a rhetorical (non-innocent) inquisitor, my favorite retort is, "You are a modeler." Anyone who ventures a projection, or imagines how a social dynamic--an epidemic, war, or migration--would unfold is running some model.
But typically, it is an implicit model in which the assumptions are hidden, their internal consistency is untested, their logical consequences are unknown, and their relation to data is unknown. But, when you close your eyes and imagine an epidemic spreading, or any other social dynamic, you are running some model or other. It is just an implicit model that you haven't written down.

This being the case, I am always amused when these same people challenge me with the question, "Can you validate your model?" The appropriate retort, of course, is, "Can you validate yours?"  
The choice is not whether to build models; it's whether to build explicit ones. 

Here's more Joshua Epstein on modelling.

by datacharmer | Saturday, July 21, 2012
| 0 comments | | Why model? @bluematterblogtwitter

Lady tasting tea - The adventures of R.A. Fisher in statistical science

Already, quite soon after he had come to Rothamstead, his presence had transformed one commonplace tea time to an historic event. It happened one afternoon when he drew a cup of tea from the urn and offered it to the lady beside him, Dr. B. Muriel Bristol, an algologist. She declined it, stating that she preferred a cup into which the milk had been poured first. “Nonsense,” returned Fisher, smiling, “Surely it makes no difference.” But she maintained, with emphasis, that of course it did. From just behind, a voice suggested, “Let’s test her.”

Fascinating anecdote from the life of R.A. Fisher. The link has more on Fisher's exact test and on whether the lady was indeed able to tell the difference between cups.