A producer of contact lenses regularly takes samples of 100 lenses and inspects them for scratches. If a lens has a single scratch, it cannot be sold. The results of 10 samples are shown below:
Sample # 1 2 3 4 5 6 7 8 9 10
# scratched 3 2 0 1 2 2 1 0 1 2
What are the lower and upper 3-sigma control limits?