Things that have heads include:
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Hammers, knives, toothpaste,arrow heads,ext.
He measured the heads of people and looked for patterns.
The side heads is slightly heavier giving it a greater likely hood of landing on tails.
means that the effect will occur at least 95% of the time... for example, if you toss a coin 20 times and get heads 19 times, you could say that the bias of the coin to land on heads is significant, since 19/20 = 95%