Answer:
The 95% confidence interval is [tex] 17.932 < \mu < 20 + 22.068[/tex]
Step-by-step explanation:
From the question we are told that
The population standard deviation is [tex]\sigma =7 \ inches[/tex]
The sample size is n = 20
The sample mean is [tex]\= x = 20[/tex]
From the question we are told the confidence level is 95% , hence the level of significance is
[tex]\alpha = (100 - 95 ) \%[/tex]
=> [tex]\alpha = 0.05[/tex]
Generally from the normal distribution table the critical value of [tex]\frac{\alpha }{2}[/tex] is
[tex]Z_{\frac{\alpha }{2} } = 1.96[/tex]
Generally the margin of error is mathematically represented as
[tex]E = Z_{\frac{\alpha }{2} } * \frac{\sigma }{\sqrt{n} }[/tex]
=> [tex]E = 1.96 * \frac{7 }{\sqrt{20} }[/tex]
=> [tex]E = 2.068[/tex]
Generally 95% confidence interval is mathematically represented as
[tex]\= x -E < \mu < \=x +E[/tex]
=> [tex] 20 - 2.068 < \mu < 20 + 2.068[/tex]
=> [tex] 17.932 < \mu < 20 + 22.068[/tex]
