Assuming that the incidence of each letter in a passage is independent of the incidence of the other letters, and provided m is much larger than 26, the probability that a sequence of length m will contain all 26 letters is approximately
In the context of sequences with many more elements (m) than there are symbols in the alphabet (26), we can approximate the probability that a sequence will contain all 26 letters by considering the total number of possible combinations and the likelihood of each individual symbol appearing.