A stats prof in 2011 told me to "show the denominator or shut up" and it stuck
Back in college I made a bar chart for a class project on gas prices in Ohio. I had the bars going up and a big bold percentage on top. Prof wrote one line in red pen: "out of how many stations?" I had picked 4 gas stations near campus and called it a trend.
I redo it now with n in the corner of every chart and the source line right under it. Took me years to admit that one red pen note did more than any lecture.
What small note from a teacher or editor actually changed how you look at a stat?
The prof's note was about the small sample, not the missing denominator, since "out of how many stations" is really asking how many you looked at. Same lesson in the end, just wanted to point that out.