P-Value Explainer
What does "p = 0.04" actually mean? Drag the sliders to see how sample size and the size of a gap move the p-value, then plug in your own test results below.
Hover (or tap) any part of the chart or the numbers below it to see where it comes from.
2,000
10.0%
12.0%
Gap (dot position)
+2.0 pts
Luck wobble (curve width)
0.99 pts
p-value
0.043
Significant when p < 0.05.
- The curve shows every gap you could get from luck alone if Group B and Group A truly performed the same. Its width is the luck wobble (the standard error).
- The shaded tails are the "too unlikely to be luck" zone. Together they hold 5% of the curve.
- The dot is your observed gap. The p-value is the share of the curve that sits at least as far from zero as the dot, on both sides. Dot inside a shaded tail means p is below the cutoff, so the result is significant.
- Drag people per group up and the curve squeezes. It shrinks with the square root of the sample: four times the people halves the wobble, which is why big samples can detect small gaps.
Try your own numbers
These start with example data and are linked to the sliders above: drag a slider and these update, type here and the sliders move. For three or more groups, use the Significance Calculator.
Group A
Group B