Three traps catch almost everyone. Meet them on purpose now and they'll never fool you: a stray value that drags the mean, a chart that's been quietly stretched, and a pattern that gets mistaken for a cause.
Trap One: an Outlier Drags the Mean, Not the Median
An outlier is a value sitting way out on its own — a mistake, a freak event, or something genuinely unusual. Because the mean uses every value, one outlier yanks it a long way. Take 4, 5, 5, 6 — mean and median are both 5. Now a reading comes in at 95: the mean leaps to 23, but the median is still 5. The mean is now describing a "typical" value that no actual data point is near. So whenever a dataset has a stray extreme, the median is usually the more honest middle. Drag the runaway dot in the toy and watch the mean chase it while the median holds its ground.
Trap Two: a Chopped Axis Exaggerates Tiny Differences
Here's the favourite trick of dodgy charts. Two bars: 98 and 100. If the axis starts at zero they look almost identical — because they nearly are. But start the axis at 96 and suddenly one bar is twice the height of the other. Same two numbers, wildly different impression. Chopping the bottom off the y-axis (a truncated axis) magnifies differences that are actually trivial. It's not always cheating — sometimes you genuinely need to zoom in — but you must notice it, because it's how a 2% difference gets sold as a landslide. Flick the toggle to see honest-versus-chopped on the very same data.
Trap Three: Correlation Isn't Causation
Two things can rise and fall together without one causing the other. Ice-cream sales and drownings both climb in summer — but ice cream doesn't drown anyone; hot weather drives both. When a chart shows two lines moving together your brain wants to shout "one caused the other!" — and most of the time you can't tell from the chart alone. There might be a hidden third thing (the heat), or it might be pure coincidence. Spotting a pattern is a great start; proving a cause needs a proper controlled experiment, not a suggestive graph.