To verify the single-error detection rate , observe from our theorem that in positions
2,4,6 and 8 substitution of b for a will go undetected when |a-b|=5; in position 5,
a substitution of b for a will go undetected when a and b have the same parity.
Thus in each of positions 2,4,6 and 8 there are 10 undetected error among 90
possible error while in the fifth position ,40 of the 90 possible error are undetected.