Answer:
a) 6.68% of heights less than 150 centimeters
b) 58.65% of heights between 160 centimeters and 180 centimeters
Step-by-step explanation:
When the distribution is normal, we use the z-score formula.
In a set with mean
and standard deviation
, the zscore 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 pvalue, we get the probability that the value of the measure is greater than X.
In this question, we have that:
![\mu = 162, \sigma = 8](https://tex.z-dn.net/?f=%5Cmu%20%3D%20162%2C%20%5Csigma%20%3D%208)
a) The percentage of heights less than 150 centimeters
We have to find the pvalue of Z when X = 150. 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{150 - 162}{8}](https://tex.z-dn.net/?f=Z%20%3D%20%5Cfrac%7B150%20-%20162%7D%7B8%7D)
![Z = -1.5](https://tex.z-dn.net/?f=Z%20%3D%20-1.5)
has a pvalue of 0.0668
6.68% of heights less than 150 centimeters
b) The percentage of heights between 160 centimeters and 180 centimeters
We have to find the pvalue of Z when X = 180 subtracted by the pvalue of Z when X = 160.
X = 180
![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{180 - 162}{8}](https://tex.z-dn.net/?f=Z%20%3D%20%5Cfrac%7B180%20-%20162%7D%7B8%7D)
![Z = 2.25](https://tex.z-dn.net/?f=Z%20%3D%202.25)
has a pvalue of 0.9878
X = 160
![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{160 - 162}{8}](https://tex.z-dn.net/?f=Z%20%3D%20%5Cfrac%7B160%20-%20162%7D%7B8%7D)
![Z = -0.25](https://tex.z-dn.net/?f=Z%20%3D%20-0.25)
has a pvalue of 0.4013
0.9878 - 0.4013 = 0.5865
58.65% of heights between 160 centimeters and 180 centimeters