3. The phrase highlights the fact that the study doesn't mean sleeping more will directly lead to better wages. Other factors are involved, such as the way people schedule their lives, how much sleeping time is available, and how that affects worker performances and earnings.
4. People naturally sleep longer when the sun sets earlier (according to the research).
5. The different time the sun sets within a single time zone.
6. (i) NG
7. Higher wages lead to higher home values.