Here is an example Maryland International Raceway, 10/8/2011, 11:30 am:

Actual track measurements: 69ºF, 43%RH, 30.45"Hg, calc 184 ft DA (80 ft track elevation).

Drag Times: 66ºF, 56%RH, 30.54"Hg, their calc 33 ft DA (87 ft track elevation)

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9pm
Track Measure: 54ºF, 97%RH, 30.39"Hg, calc -690 ft DA
Drag Times: 52ºF, 82%RH, 30.49"Hg, -881 ft DA

The other thing to note was that the actual performance didn't change as much as the DA might indicate. A 900 ft change in DA might indicate an ET change of 0.09 seconds (gas, normally aspirated), but nobody saw that much. That is my feeling about the equations not reflecting the actual humidity effects.
FWIW, my car went 5.778 at 11:30am and 5.794 at 9pm. (not bad)
All runs (in order) 5.778, 5.790, 5.788, 5.790, 5.792, 5.794 (lost -0.001 red)
Gas cars change more due to temp, alcohol due to humidity.