This approximation may be useful in practice. For example, consider a single page of the Guardian newspaper containing, say, 106 characters, and suppose that the typesetter flips a coin before setting each character and then deliberately mis-sets this character whenever the coin comes up heads. If the coin comes up heads with probability 10−5 on each flip, then this is the equivalent to taking n = 106 and p = 10−5 in the above example, giving that the number Sn of deliberate mistakes has the binomial distribution with parameters 106 and