Answer :
A 99% confidence interval on the population mean alcohol level in this situation is 0.0347.
A sample of 57 observations for alcohol levels randomly taken on highway 6 at 3am on Saturday, resulted in a mean of 0.057 and a variance of 0.0075 respectively.
n= 57
x=0.037
σ[tex]^{2}[/tex] = 0.0001099
σ = √σ2
=√0.0001099
σ = 0.01048
90% confidence interval,
d= 1-0.9=0.1
From z-table, [tex]z_{\frac{2}{z} }=z_{0.05}=1.645[/tex]
90% confidence interval,
δ= x±[tex]z_{\frac{\alpha }{2} }[/tex].σ/√n
= 0.037±1.645×[tex]\frac{0.01048}{\sqrt{57} }[/tex]
= [tex]0.037[/tex]±0.0023
= (0.0347, 0.0393)
Lower limit = 0.0347
Upper limit = 0.0393
Therefore, the lower limit is 0.347.
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