One way of looking at "Statistically significant" is that it's statement about confidence in measurement. Consider a couple scenarios involving unfair coins: I

One way of looking at "Statistically significant" is that it's statement about confidence in measurement. Consider a couple scenarios involving unfair coins: In scenario 1, you have a coin that's weighted towards head with a probability of 75%. You want to confirm that it really is an unfair coin, so you flip it 10 times and get 7 heads. In casual conversation, you or I might say that 75% is significantly more than 50% you get with a normal coin. However the result of your experiment isn't statistically significant; a fair coin could have easily given the same results by chance. In scenario 2, you have an unfair coin that comes up heads with probability 50.1%. You flip it one billion times, and 501 million of those are heads. Now we have the opposite situation: the difference between 50% and 50.1% is insignificant in most contexts. But the results of this experiment are unambiguous; over 1 billion flips, it would be extremely unlikely for a fair coin to show that large of a skew. So the results of our experiment are statistically significant and we can conclude that the coin really is unfair.