[Doug G]

Sounds pretty good to me, I don't claim to be an ball pressure-weight expert, but I have do have a degree in physics and have taught physics for 14 years and would give you an A for your presentation of the situation. You could've have got an A+, but you missed the part about the difference in composition of the gas inside the ball and the surrounding air (the compressor may add a few dirty molecules). But seriously - you summed it up nicely!!

We weighed our ball, inflated to 40" in size, and it came out to about 7.2 lbs. After reading the manual, it said it will weigh 10 pounds. I thought our scale was off or needed to be calibrated, but I think your findings support our scale's reading.