Here we need to know :
a) Minimum Hamming distance needed to detect 'd' errors = d + 1
b) Minimum Hamming distance needed to correct 'd' errors = 2d + 1
c) A simple parity scheme has one bit error detecting capability
In the modified parity scheme , we can detect two errors as we are using two separate parity bits ; one for checking bits at odd-numbered positions and other at even numbered positions.
Hence number of errors that can be detected = 2 (corresponding to each parity bit we have one error which can be detected)
Hence minimum hamming distance needed for error detection = d + 1 = 2 + 1 = 3
minimum hamming distance needed for error correction = 2d + 1 = 2(2) + 1 = 5