
At the end of the test, 90% of people that saw the green button clicked it, whereas 60% of the people that saw the blue button clicked it.

Now we need to ask, “If color wasn’t related to click rate, how likely was a 30% difference just by chance?” We can use statistics to calculate that probability. If there is less than a 5% probability that our results happened by chance, we have good evidence that green buttons get more clicks!

Statistically speaking, there is less than a 5% chance of that happening.

How did they calculate the probability of that happening? Thanks!
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