Mistake rib is what happens when you try to do a 2x2 rib with and odd number of stitches. The look of this stitch is similar to a 1x1 rib, but the knit columns are raised up. This is because on either side of the knit column there is a vertical row if garter stitch. Two positive attributes of this stitch is that it lays flat and is the same on both side. Mistake rib is an interesting alternative to 2x2 rib and is relatively simple to achieve.
Mistake Rib (worked flat)
Multiple of 4, -1(ex: 25, 41, ect.)
Row 1: *K2, P2*to last 3 stitch K2, P1
Mistake Rib ( in the round)
Multiple of 4, -1 (ex: 23, 39, ect.)
Row 1: *K2, P2*