Do we humans get enough amount of sleep we need?

Here is what some experts are saying...

"There is increasing evidence that there is a very strong relationship between sleep quality and physical and mental health..."A national survey of 31,044 adults revealed a link between insomnia and other sleeping problems with high blood pressure, heart failure, anxiety, and depression.Experts say that there is no evidence yet to indicate that acquiring more sleep will improve medical conditions, but some studies have shown that more sleep makes teenagers do better in school.

The US National Sleep Foundation suggests that an adult needs seven to nine hours of sleep a night. The Foundation conducted a survey in 2012 that suggested about 75% of Americans had sleeping problems, with one-third being so sleepy during the day that it affected their lives and activities.

What is the implied population?

What is the sample?

Is 75% a statistic or a parameter?Explain.