Reread my last paragraph -- you misunderstand my position (phrased for maximal irony). I care very much if my students or (hypothetical) employees misuse terminology. But the best way by far to communicate that a value changed from 10% to 12% is to say "xyz changed from 10% to 12%." I hope that the next step in the conversation is not a discussion of whether that means that the value changed by 20% or by 2%, but whether the change is important and measured precisely...

but I am a little worried that you call them z-tests instead of t-tests (even when using Gaussian critical values) (and, to belabor the point, I try to call them "Gaussian" critical values because "Normal" may be interpreted ambiguously by a non-technical reader, but I can usually tell whether someone I'm talking to means "normal" in a technical or vague sense).

:)

My apologies, I'm only an amateur statistician. I'll defer to your knowledge in that area. =) (and I'm joking here, I'm decent with the stats, just wanted to focus on the broader issue).

I don't want to get bogged down in the stats discussion because I was making a broader point and don't claim to be an expert in statistics. We could extend the example to any area where one person has more technical expertise in any certain subject than the people they are communicating with.

So, let's step outside the arena of statistics for a second. If you were teaching someone to cook, would you really explain the process using terms like a 'pinch' or a 'dash' of salt. Sure, to an expert chef or grandmother, a pinch of salt is a perfectly reasonable quantity to add to the recipe. The student just learning to cook can only guess at what that term means. That's why most recipes come with specific amounts or weights of ingredients to add, because we need a common terminology to correctly express the recipe.

Taken totally as an argument for teaching or explaining statistics, I see your point. It's far more important to discuss and quantify the significance of the change rather than simply noting that something did change and by how much.

And yeah, irony went right over my head. I blame Friday. =)

For cooking: I'd say 'pinch' or 'dash' and then clarify if the person asked for clarification. If he or she looks puzzled, I'll offer the clarification unsolicited and as naturally as possible. When I cook pancakes on the weekend with my three year old daughter, we talk about how the appearance of the edge of the pancake changes as it gets closer to being ready to be flipped. To get even further off topic -- if you like cooking, take a look at "Tartine Bread" which is damn near the pinnacle of this sort of communication.

Well, that will teach me to argue with an Econ professor! And I also find myself hungry after staring at pictures of bread on google for the past 10 minutes. Thanks for the interesting discussion. =)

bon appetit!