Re: Actual weight of 3 lb. package
I installed my first bees this year, and they were packages from Olivarez. They were both nominally 3 lb each, but I did not weigh them. One was significantly heavier than the other and both were in excellent shape (5-10 dead bees in each, live bees in apparent good health). So, was one 'short' and the other on weight or above? Were both short or both above? In the end, since I am a hobbyist, it really doesn't matter to me. I received good bees that have built up well. The queens are laying very well.
Still, the OP brings up an interesting question, one that I was glad to read and which I had not considered. In any measurement, there is error. 3 lb on one scale may read as 3.1 lb on another and 2.9, 2.6, or even 3.4 on others. Add to that uncertainty the loss of weight through water loss (respiration, depends on temperature and humidity during transit) and there's yet another variable thrown in.
Why not perform an experiment? Fill a package, weigh it. Fill a milk jug with enough water to weigh the same as the package. Put the package in the garage or shed for 2 days, weigh it and the milk jug again on the same scale. I'll bet that there will be a loss of weight for the package.
Pete. New 2013, 12 hives, zone 6a
To study and not think is a waste. To think and not study is dangerous.