  ### Home > CCAA8 > Chapter 7 Unit 3 > Lesson CC3: 7.3.3 > 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 they got and then was asked to list the ten items. The results are below.

 Remembered all $\mathbf{10}$ items? Yes No TOTAL Less than $\mathbf{7}$ hours sleep $6$ $149$ $155$ $\mathbf{7}$ to $\mathbf{9}$ hours sleep $11$ $109$ $120$ At least $\mathbf{10}$ 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 conditional 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 $\mathbf{7}$ hours sleep $\mathbf{3.9\%}$ $\mathbf{7}$ to $\mathbf{9}$ hours sleep $\mathbf{90.8\%}$ At least $\mathbf{10}$ hours sleep