1. Initial product moistures must all be the same in each set.
2. Sealed empty packages must be used as controls.
3. The heat and humidity at the storage conditions should not result in weight changes other than from moisture, i.e., no chemical changes in leavening systems.
4. The weight variation of the packages must be small with respect to net product weight. A rule of thumb is that the weight difference between the heaviest and lightest empty packages divided by the average net weight of the product must equal 0.025 or less.