You intend to estimate a population mean [tex]$\mu$[/tex] with the following sample.

[tex]\[
\begin{tabular}{|l|}
\hline
50.9 \\
\hline
26.2 \\
\hline
79.8 \\
\hline
32.7 \\
\hline
62.7 \\
\hline
45.7 \\
\hline
51.5 \\
\hline
95.5 \\
\hline
50.2 \\
\hline
22.8 \\
\hline
64.1 \\
\hline
\end{tabular}
\][/tex]

You believe the population is normally distributed. Find the [tex]$95 \%$[/tex] confidence interval. Enter your answer accurate to two decimal places.



Answer :

Certainly! Let's find the 95% confidence interval for the population mean [tex]\(\mu\)[/tex] using the given sample data. The sample consists of 11 values: [tex]\(50.9, 26.2, 79.8, 32.7, 62.7, 45.7, 51.5, 95.5, 50.2, 22.8, 64.1\)[/tex]. Here is the detailed step-by-step solution:

1. Calculate the sample mean [tex]\(\bar{x}\)[/tex]:
[tex]\[ \bar{x} \approx 52.92 \][/tex]

2. Calculate the sample standard deviation [tex]\(s\)[/tex]. Given:
[tex]\[ s \approx 22.03 \][/tex]

3. Determine the sample size [tex]\(n\)[/tex]:
[tex]\[ n = 11 \][/tex]

4. Calculate the standard error of the mean (SEM):
[tex]\[ \text{SEM} = \frac{s}{\sqrt{n}} \approx \frac{22.03}{\sqrt{11}} \approx 6.64 \][/tex]

5. For a 95% confidence interval, the z-score (critical value for standard normal distribution) is approximately 1.96.

6. Calculate the margin of error (MOE):
[tex]\[ \text{MOE} = z \cdot \text{SEM} \approx 1.96 \cdot 6.64 \approx 13.02 \][/tex]

7. Determine the confidence interval:
- Lower bound of the confidence interval:
[tex]\[ \bar{x} - \text{MOE} \approx 52.92 - 13.02 \approx 39.90 \][/tex]
- Upper bound of the confidence interval:
[tex]\[ \bar{x} + \text{MOE} \approx 52.92 + 13.02 \approx 65.94 \][/tex]

Thus, the 95% confidence interval for the population mean [tex]\(\mu\)[/tex] is approximately [tex]\((39.90, 65.94)\)[/tex].

So, we can be 95% confident that the true population mean [tex]\(\mu\)[/tex] lies within the interval [tex]\(39.90\)[/tex] to [tex]\(65.94\)[/tex].