Question

A large survey was conducted of more than 1 million people aged 30-102. It tracked them for 4 years to see the length of their average nights sleep. It found that people who slept 6 or 7 hours had a significantly lower death rates (i.e. died during the 4 years) than people who slept 8 hours or more. Based on this would you tell people who sleep 9 hours a day to sleep less if they want to live longer? Why?

Answer 1

Based on this, we would not tell people who sleep 9 hours a day to sleep less if they want to live longer.

REASON:

Here, Cause and Effrect Relationship is studied as below:
Cause: number of hours of sleep

Effect: Death rate.

In studying the above Cause and Effect relationship, we note that the Confounding Variables, i.e., the any other extra independent variables, that are having a hidden effect on the dependent variable, are not controlled.

In the above case, the Confounding Variables, which affect Death Rate are: Drinking & Smoking (For drunkers and smokers, Death rate will be high), emplyed in jobs involving high stress (For highly stressed people, Death rate will be high) etc.