Real-Life Math
You are working as a polysomnography technician. Your task tonight
is to discover a patient's sleep efficiency. Sleep efficiency is the amount
of time that a person sleeps in relation to the amount of time that they are
in bed.
For example, if you were in bed for exactly 10 hours, but you
slept for only 9 hours of that time, your sleep efficiency would be 9 / 10
x 100, or 90 percent. Ninety percent is considered good sleep efficiency.
You
attach electrodes to your patient's face and scalp. The electrodes transmit
electrical impulses to a machine. In this field, you work with a scale called
an EPOCH. When the machine is monitoring brain waves, every 10 millimeters
of paper represents 1 second of monitoring.
One EPOCH contains 30 seconds
of monitoring. Therefore, 10 x 30 millimeters of paper is 1 EPOCH.
You
get the patient hooked up and turn the lights out at 10 p.m. That is called
Time Zero. The machine monitors the patient's brain waves until you turn the
lights on the next morning at 7 a.m.
On analyzing the data, you see
that the patient did not fall asleep until 11:15 p.m., and awoke at 5:45 a.m.
He also awoke intermittently throughout the night, for a total of 21 minutes.
How
many EPOCHs were recorded between Time Zero and lights on? Using EPOCHs to
calculate the number, what is your patient's sleep efficiency?