The data told us which students were strong and which were
weak in a given subject, but we couldn't find the details we needed for meaningfully adjusting our instruction to move student achievement.
The scientists studied 24 men and women (11 of whom were
in their 20s and 13 of whom were
in their 60s) who lived for more than three weeks
in an environment with no time cues other than a
weak cycle of light and dark that was artificially set at 28 hours and that
gave the
subjects their signals for bedtime.