Ever read a study claiming "we found no evidence that X affects Y"? Sounds like a non-result, but in finance it happens all the time. The catch: "statistically insignificant" doesn't mean "zero effect." It just means the data can't rule out zero — but can't rule out a bunch of other values either.
Imagine measuring a door's height with a bent ruler: if the result is "between 1.80 and 2.20 meters," you've learned little. But a precise ruler saying "between 1.99 and 2.01 meters" tells you the door is standard. The first interval is vacuous, the second is bounded and informative.
The author proposes a simple rule: before analyzing, declare the smallest effect that would matter in practice (e.g., "a 1% rate hike changes investments by at least $10M"). Then compare that number with the confidence interval's edges. If the interval excludes that effect, you have a real finding: the effect is too small to matter. If the interval includes it, the study says nothing.
Often one side of the interval is informative, the other vacuous. Saying "no effect" hides this split. Next time you see "not significant," ask: is the interval tight enough to rule out what counts?
