Framing Effects Entry #0518 Classified Declassified

The reason an average framed as typical misleads

The mean of a skewed distribution describes nobody in it. Calling it typical smuggles in a claim about the shape that was never checked.

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Plate 367 — The eleven people below the middle

Intuition test — answer before you read on

Why can a correctly calculated average still mislead?

Average earnings in the department are forty-eight thousand. Eleven of the fourteen people earn less than that. Nothing in the figure is wrong, and the word average did not lie — the word typical, added by whoever summarised it, made a claim about the distribution that the number cannot support.

What everyone sees

An average is treated as the representative case, the value a randomly chosen member is likely to have. That holds only for roughly symmetric distributions. Where a few large values sit in a long tail, the mean drifts above the bulk of the data and stops describing anyone at all.

What is actually happening

Huff’s account of the well-chosen average sets out the basic manoeuvre: mean, median and mode of the same data can differ widely, all three are honestly called averages, and the presenter selects whichever supports the intended impression without stating which was used. Gigerenzer, Gaissmaier, Kurz-Milcke, Schwartz and Woloshin document the modern version in professional practice, showing that summary statistics reported without the distribution or the reference class lead trained readers to conclusions the data does not support. The structural point is that a single number cannot encode shape. Every summary discards the distribution, and the word chosen to introduce it — average, typical, normal, standard — quietly asserts what the discarded shape was.

Why it stays hidden

The substitution hides because the arithmetic is checkable and the framing is not. Anyone can verify the mean and nobody can verify typical, since the word has no definition to test against. Audit attention goes to the computable half, which is the half that was not doing the misleading.

A summary discards the shape. The adjective attached to it then asserts what the shape was, and adjectives are not auditable.

A summary discards the shape. The adjective attached to it then asserts what the shape was, and adjectives are not auditable.

The hidden part — entry #0518

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A summary discards the shape. The adjective attached to it then asserts what the shape was, and adjectives are not auditable.

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Sources & further reading 2
  1. Huff — how to lie with statistics
  2. Gigerenzer, Gaissmaier, Kurz-Milcke, Schwartz & Woloshin — helping doctors and patients make sense of health statistics

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