[Jensson]

> whereas for height, it's almost 1.0

You grow and shrink about 1% per day, as you get compressed when you stand up and decompress when you sleep. That is about 1.5 cm, and with a human height standard deviation is about 6cm you get around 0.25 standard deviation variation when measuring the height of a single human at different times of day, or about 4 point difference if we have 15 points per standard deviation.

[throwaway9917]

Standard deviation of human height (within a single sex) is about 7cm. If human height changes over the course of a day by 1.5cm, assuming it linearly declines over the day, that's a stddev of about 0.6cm. You also can reasonably assume that people are normally going to be measured at the doctor/researcher's office during business hours, so it's probably more like 0.4cm. The measurement error of just standing up straight or not and reading the numbers is probably more.