A simple random sample of 10 items resulted in a sample mean of 15. The population standard deviation is [tex]\sigma = 1[/tex]. Round your answers to two decimal places.

a. What is the standard error of the mean, [tex]\sigma_{\bar{x}}[/tex]?
[tex]\(\square\)[/tex]

b. At [tex]95\%[/tex] confidence, what is the margin of error?
[tex]\(\square\)[/tex]



Answer :

Let's solve the given problem step-by-step.

### Part a: Calculating the Standard Error of the Mean

The standard error of the mean (SEM) is calculated using the following formula:

[tex]\[ \sigma_{\bar{x}} = \frac{\sigma}{\sqrt{n}} \][/tex]

Where:
- [tex]\(\sigma\)[/tex] is the population standard deviation
- [tex]\(n\)[/tex] is the sample size

Given:
- [tex]\(\sigma = 1\)[/tex]
- [tex]\(n = 10\)[/tex]

Let's plug in these values into the formula:

[tex]\[ \sigma_{\bar{x}} = \frac{1}{\sqrt{10}} \][/tex]

Calculate [tex]\(\sqrt{10}\)[/tex]:

[tex]\[ \sqrt{10} \approx 3.162 \][/tex]

Then the standard error:

[tex]\[ \sigma_{\bar{x}} = \frac{1}{3.162} \approx 0.32 \][/tex]

So, the standard error of the mean is approximately:

[tex]\[ 0.32 \][/tex]

### Part b: Calculating the Margin of Error at 95% Confidence

The margin of error (ME) at a given confidence level is calculated using the formula:

[tex]\[ ME = z \times \sigma_{\bar{x}} \][/tex]

Where:
- [tex]\(z\)[/tex] is the z-value corresponding to the desired confidence level
- [tex]\(\sigma_{\bar{x}}\)[/tex] is the standard error of the mean

For a 95% confidence level, the z-value is approximately 1.96.

Given:
- [tex]\(\sigma_{\bar{x}} = 0.32\)[/tex]
- [tex]\(z = 1.96\)[/tex]

Let's plug in these values into the formula:

[tex]\[ ME = 1.96 \times 0.32 \][/tex]

Calculate the margin of error:

[tex]\[ ME \approx 1.96 \times 0.32 \approx 0.63 \][/tex]

So, the margin of error at 95% confidence is approximately:

[tex]\[ 0.63 \][/tex]

### Summary of Results
a. The standard error of the mean, [tex]\(\sigma_{\bar{x}}\)[/tex], is [tex]\(0.32\)[/tex].

b. The margin of error at 95% confidence is [tex]\(0.63\)[/tex].