Final answer:
Nine-year-old Allison needs a little more than 9 hours of sleep each night, as children her age generally require between 9 and 11 hours of sleep according to the National Sleep Foundation.
Step-by-step explanation:
Nine-year-old Allison needs a little more than 9 hours of sleep per night. While sleep requirements vary with age, young children generally need more sleep than adults. According to the National Sleep Foundation, sleep recommendations for school-age children (6-13 years) is between 9 and 11 hours of sleep each night. As children grow into teenagers, they still require more sleep than adults.
On average, teens need about 8 to 10 hours of sleep per night, considering a study shows a mean of 8.9 hours for teenagers. For adults, the required amount of sleep declines further to 7-9 hours, with many not meeting this requirement due to lifestyle and work demands, potentially accruing a sleep debt.