To earn a fitness award, your average heart rate while walking must be between 80 and 89 beats per minute, inclusive. Suppose you recorded 85, 81, and 87 beats per minute on your first three recordings. What are the possible heart rates you can have on the fourth and final recording in order to earn a fitness award?

Based on the first three (3) recordings, your average heart rate in beats per minute is approximately 84 bpm (mean). Calculating for the standard deviation of the samples, we get about 2.5 bpm. To give the possible heart rates on the fourth, we may solve for the range:

Upper Range = Mean + Standard Deviation = 84 + 2.5 = 86.5 bpm or 87 bpm
Lower Range = Mean - Standard Deviation = 84 - 2.5 = 81.5 bpm or 82 bpm

Therefore the fourth and final recording will likely to fall in the range of 82 - 87 beats per minute. You will win the fitness award!

ANSWER: 82-87 beats per minute