Answer:
a) The difference is of 35 beats per minute.
b) So 3.07 standard deviations below the mean.
c) Z = -3.07.
Step-by-step explanation:
Z-score:
In a set with mean
and standard deviation
, the z-score of a measure X is given by:
![Z = \frac{X - \mu}{\sigma}](https://tex.z-dn.net/?f=Z%20%3D%20%5Cfrac%7BX%20-%20%5Cmu%7D%7B%5Csigma%7D)
The Z-score measures how many standard deviations the measure is from the mean. After finding the Z-score, we look at the z-score table and find the p-value associated with this z-score. This p-value is the probability that the value of the measure is smaller than X, that is, the percentile of X. Subtracting 1 by the p-value, we get the probability that the value of the measure is greater than X.
In this question:
Mean
, standard deviation ![\sigma = 11.4](https://tex.z-dn.net/?f=%5Csigma%20%3D%2011.4)
a. What is the difference between the pulse rate of 39 beats per minute and the mean pulse rate of the? females?
39 - 74 = -35
The difference is of 35 beats per minute.
b. How many standard deviations is that? [the difference found in part? (a)?
|Z| when X = 39. So
![Z = \frac{X - \mu}{\sigma}](https://tex.z-dn.net/?f=Z%20%3D%20%5Cfrac%7BX%20-%20%5Cmu%7D%7B%5Csigma%7D)
![Z = \frac{39 - 74}{11.4}](https://tex.z-dn.net/?f=Z%20%3D%20%5Cfrac%7B39%20-%2074%7D%7B11.4%7D)
![Z = -3.07](https://tex.z-dn.net/?f=Z%20%3D%20-3.07)
|Z| = 3.07
So 3.07 standard deviations below the mean.
c. Convert the pulse rate of 39 beats per minutes to a z score.
From item b. above, Z = -3.07.