How long a student sleeps affects test scores? Sleep is essential for brain development the general guidelines are that age 13-should have 9-11 hours sleep every night, and teenagers 14-17 should get
between 8 and 10 hours, young adults aged 18-25 should sleep 7-9 hours a night. Not surprisingly a number of studies have shown that the lack of sleep directly affects children's test score. Researchers recorded
sleep patterns of 621 firs year university students in Belgium and later found that those students who had better sleep habits performed better on their exam specifically the test scores of those students who sleptat
least seven hours per night where about 10 percent higher than those who didn't get that much sleep.
In the above study to determine whether how long a student sleeps affects test scores, the independent variable is the length of time spent sleeping while the dependent variable is the test score. In the study the
students who slept at least seven hours per night and who didn't sleep for seven hours are example of the independent variable, the result of 10 percent higher than those who didn't get that much sleep is example of
Dependent variable.

what could be a possible extraneous variable?