"That which is measured, improves"
It is possible that these quotes were inspired by Lord Kelvin who is frequently attributed the quote: "If you can not measure it, you can not improve it."
It is not an exact logical match, but it certainly expresses a similar idea regarding the importance of empirical measurement.
The first example of that quote from Thomas S Monson that I could find is directly preceded by the phrase A cardinal principle of industrial management teaches:, so it sounded like he felt it was a truth that was so widely known and accepted that it didn't need a specific citation.