The number of knots per square inch (KPSI) would be an important factor for finer rugs such as Nain, Isfahan, and Quom. Tribal rugs have their own character in colors and patterns and not much influenced by a tight weave. However, if you count the knots in one inch to the direction of the width of the rug, and then multiply it by itself, you will get an estimate of the KPSI. As mentioned before, the warps sit next to each other in a parallel position, so getting an exact knot count would be a bit tricky for you. At any rate, I would not be at all concerned with these numbers for a rug like yours. Enjoy it as it is, whatever the KPSI.