### Home > CC3 > Chapter 7 > Lesson 7.3.3 > Problem 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 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.