Answer:
(a) 0.14%
(b) 2.28%
(c) 48%
(d) 68%
(e) 34%
(f) 50%
Step-by-step explanation:
Let <em>X</em> be a random variable representing the prices paid for a particular model of HD television.
It is provided that <em>X</em> follows a normal distribution with mean, <em>μ</em> = $1600 and standard deviation, <em>σ</em> = $100.
(a)
Compute the probability of buyers who paid more than $1900 as follows:
![P(X>1900)=P(\frac{X-\mu}{\sigma}>\frac{1900-1600}{100})](https://tex.z-dn.net/?f=P%28X%3E1900%29%3DP%28%5Cfrac%7BX-%5Cmu%7D%7B%5Csigma%7D%3E%5Cfrac%7B1900-1600%7D%7B100%7D%29)
![=P(Z>3)\\=1-P(Z](https://tex.z-dn.net/?f=%3DP%28Z%3E3%29%5C%5C%3D1-P%28Z%3C3%29%5C%5C%3D1-0.99865%5C%5C%3D0.00135%5C%5C%5Capprox%200.0014)
*Use a <em>z</em>-table.
Thus, the approximate percentage of buyers who paid more than $1900 is 0.14%.
(b)
Compute the probability of buyers who paid less than $1400 as follows:
![P(X](https://tex.z-dn.net/?f=P%28X%3C1400%29%3DP%28%5Cfrac%7BX-%5Cmu%7D%7B%5Csigma%7D%3C%5Cfrac%7B1400-1600%7D%7B100%7D%29)
![=P(Z](https://tex.z-dn.net/?f=%3DP%28Z%3C-2%29%5C%5C%3D1-P%28Z%3C2%29%5C%5C%3D1-0.97725%5C%5C%3D0.02275%5C%5C%5Capprox%200.0228)
*Use a <em>z</em>-table.
Thus, the approximate percentage of buyers who paid less than $1400 is 2.28%.
(c)
Compute the probability of buyers who paid between $1400 and $1600 as follows:
![P(1400](https://tex.z-dn.net/?f=P%281400%3CX%3C1600%29%3DP%28%5Cfrac%7B1400-1600%7D%7B100%7D%3C%5Cfrac%7BX-%5Cmu%7D%7B%5Csigma%7D%3C%5Cfrac%7B1600-1600%7D%7B100%7D%29)
![=P(-2](https://tex.z-dn.net/?f=%3DP%28-2%3CZ%3C0%29%5C%5C%3DP%28Z%3C0%29-P%28Z%3C-2%29%5C%5C%3D0.50-0.0228%5C%5C%3D0.4772%5C%5C%5Capprox%200.48)
*Use a <em>z</em>-table.
Thus, the approximate percentage of buyers who paid between $1400 and $1600 is 48%.
(d)
Compute the probability of buyers who paid between $1500 and $1700 as follows:
![P(1500](https://tex.z-dn.net/?f=P%281500%3CX%3C1700%29%3DP%28%5Cfrac%7B1500-1600%7D%7B100%7D%3C%5Cfrac%7BX-%5Cmu%7D%7B%5Csigma%7D%3C%5Cfrac%7B1700-1600%7D%7B100%7D%29)
![=P(-1](https://tex.z-dn.net/?f=%3DP%28-1%3CZ%3C1%29%5C%5C%3DP%28Z%3C1%29-P%28Z%3C-1%29%5C%5C%3D0.84134-0.15866%5C%5C%3D0.68268%5C%5C%5Capprox%200.68)
*Use a <em>z</em>-table.
Thus, the approximate percentage of buyers who paid between $1500 and $1700 is 68%.
(e)
Compute the probability of buyers who paid between $1600 and $1700 as follows:
![P(1600](https://tex.z-dn.net/?f=P%281600%3CX%3C1700%29%3DP%28%5Cfrac%7B1600-1600%7D%7B100%7D%3C%5Cfrac%7BX-%5Cmu%7D%7B%5Csigma%7D%3C%5Cfrac%7B1700-1600%7D%7B100%7D%29)
![=P(0](https://tex.z-dn.net/?f=%3DP%280%3CZ%3C1%29%5C%5C%3DP%28Z%3C1%29-P%28Z%3C0%29%5C%5C%3D0.84134-0.50%5C%5C%3D0.34134%5C%5C%5Capprox%200.34)
*Use a <em>z</em>-table.
Thus, the approximate percentage of buyers who paid between $1600 and $1700 is 34%.
(f)
Compute the probability of buyers who paid between $1600 and $1900 as follows:
![P(1600](https://tex.z-dn.net/?f=P%281600%3CX%3C1900%29%3DP%28%5Cfrac%7B1600-1600%7D%7B100%7D%3C%5Cfrac%7BX-%5Cmu%7D%7B%5Csigma%7D%3C%5Cfrac%7B1900-1600%7D%7B100%7D%29)
![=P(0](https://tex.z-dn.net/?f=%3DP%280%3CZ%3C3%29%5C%5C%3DP%28Z%3C3%29-P%28Z%3C0%29%5C%5C%3D0.99865-0.50%5C%5C%3D0.49865%5C%5C%5Capprox%200.50)
*Use a <em>z</em>-table.
Thus, the approximate percentage of buyers who paid between $1600 and $1900 is 50%.