Tia  Gottlieb

Tia Gottlieb


Significant? You Really Mean Detectable

You might see me twitch whenever I hear a colleague say “significant” when they clearly mean “statistically significant” (which in fact has nothing to do with being “clinically significant” or “scientifically significant”). These cognitive hiccups jar me out of my colleague’s otherwise careful scientific narrative. I get a little concerned that they might have fundamentally misunderstood their analysis results — not something you or your clients want to hear from your statistician!

So here’s my short attempt to help correct two common phrases about research findings. They’re wrong because of how they are commonly misinterpreted.

I’ll share each wrong phrase, its interpretations, and a better phrase. If you’re interested, I provide detailed reasoning on Wrong Phrase 1 at the end. (As an exercise, you should try applying similar reasoning to Wrong Phrase 2.)

Wrong Phrase 1: Decrease/Increase

There was a significant decrease of size D in the outcome.

two seagulls on a beach rock, side by side, one perched a tad higher than the other


  • Common Misinterpretation: There was a scientifically or clinically significant, important, meaningful, or useful decrease of size D in the outcome.
  • A Correct Interpretation:* There was significant statistical evidence that a true, unknown change (i.e., decrease/increase) in the mean outcome exists that is not null (e.g., not zero). If the study was properly designed and executed, then this evidence suggests that the change we’d calculated from the sample (i.e., a decrease), which we’d denoted as D, is a good estimate of the true, unknown change, which we denote as U.

#data-science #statistics #hypothesis-testing #machine-learning #clinical-trials

Significant? You Really Mean Detectable