Poisson distribution

This is e^-x.

You may have 10 heads in each 10 times.

P(X=10)=9.765625E-4≒9/10000

This is about 0.09%, and it is almost Zero.

This is Poisson distribution.

p = λ / n

This is called Poisson limit theorem, and binomial distribution is Bernoulli trial.

x=1000 heads, n=1000 times, p=0.5(heads or tails), f=9.33E-302

∴