Statistical Significance
If something is statistically significant it means that it is unlikely to have happened by chance.
For example, if you tossed a coin 1,000 times and each time it came up tails you would think that was pretty strange.
You might think there was something more than chance at work. It is not what you would expect.
But what would you expect?
500 heads and 500 tails?
What if you got 498 heads and 502 tails?
50 heads and 950 tails?
Where would you draw the line between accepting a result as "chance" and crying "foul"?
There is statistical theory which addresses this problem. If something is said to be "significant at 1%" it means that there is a less than 1% probability of it happening by chance. That is, most likely, it DID NOT HAPPEN BY CHANCE - something else was at work.
If something is "significant at 5%" it means that there is a less than 5% probability of it happening by chance. Not very likely.
Sometimes things are quoted as being "significant at 10%".
Which is the more significant - something significant at 10% or something significant at 1%?
Answer: Something significant at 1%.