I believe the balls used by the Colts act as controls. 12 out of 12 of the Colts balls were within the specified PSI. For the Patriots 11 of 12 were out of the specified PSI.
The Colts balls don’t act as controls, since you dont know the starting conditions, or the specifics of when they were checked. Lots of rumor and assumption, and the reports only say that the Colts balls were checked at some point in time… Not necessarily even more than once.
That said, a drop of *temperature alone* in the footballs from 75°F two 50°F would give them a change of -1.27 PSI.
If the balls were at 75°F to begin with, and anywhere within the one PSI wide guidelines, by half time they would have been out of spec. Add to that the effect of having been wet, and you’ve got another half PSI or so loss of pressure.
These values have been confirmed experimentally many times in the last week.
The Colts balls may have simply not been measured with any significant precision, the information we received may be wrong, or the Colts balls were simply inflated outdoors or after having been outdoors for a length of time and were never at room temperature at all. Being kept in the hold of the bus and then topped off just before submission would account for it even if they had been properly measured.