It may be safe to assume that the EDC mechanism will not correct an erroneous bit

in a byte that contains more than one bit in error.

If one of multiple bit errors are corrected, the byte itself will still be in error.

Practically speaking, there is little purpose correcting one of multiple errors.

Also, there is the problem of accurately detecting multiple bit error numbers.

Hence, if the probability of the byte being error-free after correction is

the sum of the binomial probabilities of zero and one errors,

then the probability of 2 bits in error is

the probability of 3 bits in error is

and so on..