Problem

Assume that a sample is used to estimate a population mean $\mu$. Find the $95 \%$ confidence interval for a sample of size 58 with a mean of 44.4 and a standard deviation of 17.2. Enter your answer as an open-interval (i.e., parentheses) accurate to 3 decimal places. \[ 95 \% \text { C.I. }= \]

Solution

Step 1 :Given that the sample size \(n = 58\), the sample mean \(\bar{x} = 44.4\), and the standard deviation \(\sigma = 17.2\).

Step 2 :The z-score for a 95% confidence interval is approximately \(z = 1.96\).

Step 3 :The formula for a confidence interval is given by \(\bar{x} \pm z \frac{\sigma}{\sqrt{n}}\).

Step 4 :Substitute the given values into the formula to find the margin of error, which is \(4.426602464566966\).

Step 5 :Subtract the margin of error from the sample mean to find the lower bound of the confidence interval, which is \(39.97339753543303\).

Step 6 :Add the margin of error to the sample mean to find the upper bound of the confidence interval, which is \(48.82660246456697\).

Step 7 :\(\boxed{\text{The 95% confidence interval for a sample of size 58 with a mean of 44.4 and a standard deviation of 17.2 is approximately (39.973, 48.827).}}\)

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Source: https://solvelyapp.com/problems/18213/

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