Answer:a
a
![336.04 < \mu < 443.96](https://tex.z-dn.net/?f=336.04%20%20%20%20%3C%20%20%5Cmu%20%3C%20443.96)
b
The margin of error will increase
c
The margin of error will decreases
d
The 99% confidence interval is ![0.4107 < p < 0.4293](https://tex.z-dn.net/?f=0.4107%20%3C%20%20p%20%20%3C%200.4293)
Step-by-step explanation:
From the question we are told that
The sample size ![n = 19](https://tex.z-dn.net/?f=n%20%3D%20%2019)
The sample mean is
The standard deviation is ![\sigma = \$ \ 120](https://tex.z-dn.net/?f=%5Csigma%20%3D%20%20%5C%24%20%5C%20%20120)
Given that the confidence level is 95% then the level of significance is mathematically represented as
![\alpha = 100 - 95](https://tex.z-dn.net/?f=%5Calpha%20%3D%20100%20-%20%2095)
![\alpha = 5 \%](https://tex.z-dn.net/?f=%5Calpha%20%20%3D%20%205%20%5C%25)
![\alpha = 0.05](https://tex.z-dn.net/?f=%5Calpha%20%20%3D%20%200.05)
Next we obtain the critical value of
from the normal distribution table
So
![Z_{\frac{\alpha }{2} } = 1.96](https://tex.z-dn.net/?f=Z_%7B%5Cfrac%7B%5Calpha%20%7D%7B2%7D%20%7D%20%3D%20%201.96)
The margin of error is mathematically represented as
![E = Z_{\frac{\alpha }{2} } * \frac{\sigma}{\sqrt{n} }](https://tex.z-dn.net/?f=E%20%3D%20%20Z_%7B%5Cfrac%7B%5Calpha%20%7D%7B2%7D%20%7D%20%2A%20%20%5Cfrac%7B%5Csigma%7D%7B%5Csqrt%7Bn%7D%20%7D)
=> ![E = 1.96 * \frac{120}{\sqrt{19} }](https://tex.z-dn.net/?f=E%20%3D%201.96%20%2A%20%20%5Cfrac%7B120%7D%7B%5Csqrt%7B19%7D%20%7D)
=> ![E = 53.96](https://tex.z-dn.net/?f=E%20%3D%2053.96)
The 95% confidence interval is
![\= x - E < \mu < \= x + E](https://tex.z-dn.net/?f=%5C%3D%20x%20%20-%20%20E%20%20%3C%20%20%5Cmu%20%3C%20%5C%3D%20x%20%20%2B%20%20E)
=> ![390 - 53.96 < \mu < 390 - 53.96](https://tex.z-dn.net/?f=390%20%20-%20%20%2053.96%20%20%20%3C%20%20%5Cmu%20%3C%20390%20%20-%20%20%2053.96)
=> ![336.04 < \mu < 443.96](https://tex.z-dn.net/?f=336.04%20%20%20%20%3C%20%20%5Cmu%20%3C%20443.96)
When the confidence level increases the
also increases which increases the margin of error hence the confidence level becomes wider
Generally the sample size mathematically varies with margin of error as follows
![n \ \ \alpha \ \ \frac{1}{E^2 }](https://tex.z-dn.net/?f=n%20%20%5C%20%20%5C%20%5Calpha%20%20%5C%20%5C%20%20%5Cfrac%7B1%7D%7BE%5E2%20%7D)
So if the sample size increases the margin of error decrease
The sample proportion is mathematically represented as
![\r p = \frac{210}{500}](https://tex.z-dn.net/?f=%5Cr%20p%20%20%3D%20%20%5Cfrac%7B210%7D%7B500%7D)
![\r p = 0.42](https://tex.z-dn.net/?f=%5Cr%20p%20%20%3D%200.42)
Given that the confidence level is 0.99 the level of significance is ![\alpha = 0.01](https://tex.z-dn.net/?f=%5Calpha%20%3D%20%200.01)
The critical value of
from the normal distribution table is
![Z_{\frac{\alpha }{2} } = 2.58](https://tex.z-dn.net/?f=Z_%7B%5Cfrac%7B%5Calpha%20%7D%7B2%7D%20%7D%20%20%3D%20%202.58)
Generally the margin of error is mathematically represented as
![E = Z_{\frac{\alpha }{2} }* \sqrt{ \frac{\r p (1- \r p )}{n} }](https://tex.z-dn.net/?f=E%20%3D%20%20Z_%7B%5Cfrac%7B%5Calpha%20%7D%7B2%7D%20%7D%2A%20%20%5Csqrt%7B%20%5Cfrac%7B%5Cr%20p%20%281-%20%5Cr%20p%20%29%7D%7Bn%7D%20%7D)
=> ![E = 0.42 * \sqrt{ \frac{0.42 (1- 0.42 )}{ 500} }](https://tex.z-dn.net/?f=E%20%3D%20%200.42%20%2A%20%20%5Csqrt%7B%20%5Cfrac%7B0.42%20%281-%200.42%20%29%7D%7B%20500%7D%20%7D)
=> ![E = 0.0093](https://tex.z-dn.net/?f=E%20%3D%20%200.0093)
The 99% confidence interval is
![\r p - E < p < \r p + E](https://tex.z-dn.net/?f=%5Cr%20p%20%20-%20%20E%20%3C%20%20p%20%20%3C%20%5Cr%20p%20%20%2B%20%20E)
![0.42 - 0.0093 < p < 0.42 + 0.0093](https://tex.z-dn.net/?f=0.42%20%20-%20%200.0093%20%3C%20%20p%20%20%3C%200.42%20%20%2B%20%200.0093)
![0.4107 < p < 0.4293](https://tex.z-dn.net/?f=0.4107%20%3C%20%20p%20%20%3C%200.4293)