Average time for sex
The average time for each couple (that is, averaged across all the times for the partner had sex) ranged from 33 seconds to 44 minutes. That is an 80-fold difference.
It is clear there is no one “normal” amount of time to have sex. The average (median, technically) across all couples, though, was 5.4 minutes. This means that if you line up the 500 couples from shortest sex to longest sex, the middle couple goes for an average of 5.4 minutes each time.