A sample of 14 randomly selected commuters in Chicago had an average commuting time of 39 minutes, with a standard deviation of 9.4 minutes. Find the lower limit of the 99% confidence interval of the true (population) mean. Round your answer to one place after the decimal point.

A sample of 14 randomly selected commuters in Chicago had an average commuting time of 39 minutes with a standard deviation of 94 minutes Find the lower limit o class=

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Given the confidence interval formular

[tex]\begin{gathered} CI=\bar{x}\pm MOE \\ \bar{x}\Rightarrow\operatorname{mean} \\ \text{MOE}\Rightarrow\text{Margin of error} \\ CI=\text{confidence interval} \end{gathered}[/tex]

Calculate the Margin of error

[tex]\begin{gathered} \text{MOE}=\text{Critical value }\times SE \\ \text{where} \\ SE=\frac{\sigma}{\sqrt[]{n}} \\ \sigma=9.4 \\ n=14 \end{gathered}[/tex][tex]SE=\frac{9.4}{\sqrt[]{14}}=\frac{9.4}{3.7417}=2.5122[/tex][tex]C.V\text{ for 99\% confidence significant level =}2.58[/tex]

Thus, the margin of error is

[tex]\begin{gathered} \text{MOE}=CV\times SE \\ =2.58\times2.5122 \\ =6.48 \end{gathered}[/tex]

The confidence interval from the confidence interval formula will be

[tex]\begin{gathered} CI=\bar{x}\pm MOE \\ =39\pm6.48 \\ =32.52<39<45.48 \end{gathered}[/tex]

Hence, the lower limit of the confidence interval will be 32.52