R..
There is a very wide range for what is 'normal' as far as development goes. My DD was sitting without support by the time she was 3 months old, pulling herself to standing when she was 5 months, scooting around 5 months, crawling around 6, and has been walking since she was 9 months. She is also in the 'normal' range. I wouldn't be too concerned. My ex-roomate's baby started crawling when she was about 11 months old, and was walking at 14 months. She is 2 now and completely 'normal'. :)