Find the odd letter group: RTW, QOM, IKG, BDF.

RTW is the odd group.

With A = 1, QOM is 17, 15, 13; IKG is 9, 11, 7; BDF is 2, 4, 6.

QOM and IKG are all odd positions, and BDF are all even positions.

R, T, W are 18, 20, 23, mixing even and odd positions.

So the group of mixed parity stands apart.