In a study investigating sleep deprivation, which of the following would produce interval level data?
Ranking five daily activities from 'least exhausting' to 'most exhausting'
Classifying participants' morning alertness as 'fully alert', 'slightly drowsy', or 'very fatigued'
Measuring the exact time in minutes and seconds it takes for a participant to fall asleep
Recording participants' detailed written descriptions of how they feel upon waking
