Empirical testing with the net down

24 January, 2013 at 15:59 | Posted in Statistics & Econometrics | Leave a comment

truthversusprecisionSuppose you test a highly confirmed hypothesis, for example, that the price elasticity of demand is negative. What would you do if the computer were to spew out a positive coefficient? Surely you would not claim to have overthrown the law of demand … Instead, you would rerun many variants of your regression until the recalcitrant computer finally acknowledged the sovereignty of your theory …

Only the naive are shocked by such soft and gentle testing … Easy it is. But also wrong, when the purpose of the exercise is not to use a hypothesis, but to determine its validity …

Econometric tests are far from useless. They are worth doing, and their results do tell something … But many economists insist that economics can deliver more, much more, than merely, more or less, plausible knowledge, that it can reach its results with compelling demonstrations. By such a standard how should one describe our usual way of testing hypotheses? One possibility is to interpret it as Blaug [The Methodology of Economics, 1980, p. 256] does, as ‘playing tennis with the net down’ …

Perhaps my charge that econometric testing lacks seriousness of purpose is wrong … But regardless of  the cause, it should be clear that most econometric testing is not rigorous. Combining such tests with formalized theoretical analysis or elaborate techniques is another instance of the principle of the strongest link. The car is sleek and elegant; too bad the wheels keep falling off.

 

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