Complete Question
The complete question is shown on the first uploaded image
Answer:
The 90% confidence interval is [tex][108.165 ,112.895][/tex]
The 95% confidence interval is [tex][107.7123 ,113.3477][/tex]
The correct option is D
Step-by-step explanation:
From the question we are told that
The sample size is n = 48
The sample mean is [tex]\= x = \$ 110.53[/tex]
The standard deviation is [tex]\sigma = \$ 9.96[/tex]
Considering first question
Given that the confidence level is 90% then the level of significance is mathematically represented as
[tex]\alpha = (100 - 90)\%[/tex]
[tex]\alpha = 0.10[/tex]
The critical value of [tex]\frac{\alpha }{2}[/tex] from the normal distribution table is
[tex]Z_{\frac{\alpha }{2} } = 1.645[/tex]
Generally the margin of error is mathematically represented as
[tex]E = ZZ_{ \frac{x}{y} } * \frac{\sigma}{ \sqrt{n} }[/tex]
[tex]E = 1.645 * \frac{9.96}{ \sqrt{ 48} }[/tex]
[tex]E = 2.365[/tex]
The 90% confidence interval is
[tex]\= x - E < \mu < \= x + E[/tex]
=> [tex]110.53 - 2.365 < \mu < 110.53 + 2.365[/tex]
=> [tex]108.165 < \mu < 112.895[/tex]
Considering second question
Given that the confidence level is 95% then the level of significance is mathematically represented as
[tex]\alpha = (100 - 95)\%[/tex]
[tex]\alpha = 0.05[/tex]
The critical value of [tex]\frac{\alpha }{2}[/tex] from the normal distribution table is
[tex]Z_{\frac{\alpha }{2} } = 1.96[/tex]
Generally the margin of error is mathematically represented as
[tex]E = Z_{ \frac{x}{y} } * \frac{\sigma}{ \sqrt{n} }[/tex]
[tex]E = 1.96 * \frac{9.96}{ \sqrt{ 48} }[/tex]
[tex]E = 2.8177[/tex]
The 95% confidence interval is
[tex]\= x - E < \mu < \= x + E[/tex]
=> [tex]110.53 - 2.8177 < \mu < 110.53 + 2.8177[/tex]
=> [tex]107.7123 < \mu < 113.3477[/tex]
