### Home > ACC7 > Chapter cc37 > Lesson cc37.3.3 > Problem7-111

7-111.

Researchers have determined that teenagers’ memories are negatively affected by getting less than 10 hours of sleep. Being good scientists, the math students at North Middle School were skeptical, so they did their own study. They asked 300 students to memorize 10 objects. The next day, each student was asked how much sleep he or she got and then was asked to list the ten items. The results are below.

 Remembered all 10 items? Yes No TOTAL Less than 7 hours sleep 6 149 155 7-9 hours sleep 11 109 120 At least 10 hours sleep 5 20 25 TOTAL 22 278 300

Make a conditional relative frequency table to determine if there is an association between hours of sleep and memory. Homework Help ✎

In order to make a relative frequency table, you must first decide which variable is independent and which is dependent.

Remembering depends on how many hours of sleep a student gets so the independent variable is hours of sleep.

The frequencies should be calculated based on row totals.

 Remembered all 10 items? Yes No Less than 7 hours sleep 3.9% 7-9 hours sleep 90.8% At least 10 hours sleep