Final answer:
The study does not conclusively prove that more sleep causes increased happiness due to the principle of correlation not equating to causation. Factors contributing to happiness are numerous and varied, extending beyond just sleep.
Step-by-step explanation:
The study does not prove that getting more hours of sleep will make people happier. This is because the principle of correlation does not imply causation. Correlation indicates a relationship between two variables, but it does not establish that one variable causes the other to occur. It is important to recognize the difference. For instance, there may be a correlation between sleep duration and mood, but this does not necessarily mean that more sleep causes increased happiness. Happiness can be influenced by many different factors apart from sleep, such as personal relationships, job satisfaction, health, and more.
The principle of correlation merely identifies a pattern where two variables may move in tandem. In contrast, the principle of causation would require a demonstration that changes in one variable directly cause changes in the other, which would typically require controlled experimental studies and not mere observational studies.