Control limit for bottle packing

What is the formula to set up limit for checkweigher rejection during bottle packing. I am looking for number of tablet or weight to set in check weigher for on line rejection. All following variables should be considered appropriately. Limit should be in number of tablet not be less or more.

  1. Variation in bottle weight.
  2. Average weight of tablet
  3. Weight variation in tablets
  4. Size of pack i.e. 30 count, 50 count, 100, count, 500 count etc…
  5. Size of bottle 50 cc, 80 cc, 100 cc etc…

Pls. suggest best way to control tablet count within +/- 2 tablets without pseudo rejection.