Final answer:
Newborns have the longest average sleep time.
Step-by-step explanation:
The question asks which group has the longest average sleep time - teenagers, children aged 6 to puberty, newborns, or people over age 65. Based on the information given, we can determine the answer by comparing the average sleep times of these groups.
In the study, a sample of 16 teenagers had a mean sleep time of 8.9 hours, while a sample of 12 adults had a mean sleep time of 6.9 hours. This indicates that teenagers have a longer average sleep time than adults.
From the additional information provided, we can also see that newborns sleep the most, with an average of 12-18 hours per night, which is higher than the average sleep time of teenagers. Therefore, the correct answer is newborns have the longest average sleep time.