Since nap time averages 3 hrs, and can vary by 30 minutes (0.5 hrs), then nap time = 3 ± 0.25 hrs
Since night time sleep averages 12 hrs, and can vary by 30 minutes (0.5 hrs), then night time sleep = 12 ± 0.25 hrs
Minimum nap and night time sleep = 2.75 + 11.75 = 14.5 hrs
Maximum nap and night time sleep = 3.25 + 12.25 = 15.5 hrs
Nap and night time sleep = 15 ± 0.5 hrs
Total sleep time averages 15 hrs and can vary by 1 hr (1/2 hr above or below 15 hrs)
