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7-111.

Researchers have determined that teenagers’ memories are negatively affected by getting less than hours of sleep. Being good scientists, the math students at North Middle School were skeptical, so they did their own study. They asked students to memorize 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 items?

Yes

No

TOTAL

Less than hours sleep

 hours sleep

At least hours sleep

TOTAL

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