You have taken a random sample of size n = 19 from a normal population that has a population mean of μ=50 and a population standard deviation of a = 15. Your sample, which is Sample 1 in the table below, has a mean of x=45.3. (In the table, Sample 1 is written "S1", Sample 2 is written "S2", etc.) (a) Based on Sample 1, graph the 75% and 90% confidence intervals for the population mean. Use 1.150 for the critical value for the 75% confidence interval, and use 1.645 for the critical value for the 90% confidence interval. (If necessary, consult a list of formulas.) • Enter the lower and upper limits on the graphs to show each confidence interval. Write your answers with one decimal place. • For the points (and ◆), enter the population mean, μ = 50.

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**Educational Text and Explanation of Graphs**

You have taken a random sample of size \( n = 19 \) from a normal population that has a population mean of \( \mu = 50 \) and a population standard deviation of \( \sigma = 15 \). Your sample, which is Sample 1 in the table below, has a mean of \( \bar{x} = 45.3 \).

### Instructions:

**(a)** Based on Sample 1, graph the 75% and 90% confidence intervals for the population mean. Use 1.150 for the critical value for the 75% confidence interval, and use 1.645 for the critical value for the 90% confidence interval.

- Enter the lower and upper limits on the graphs to show each confidence interval. Write your answers with one decimal place.
- For the points (\(\color{red} \bullet\) and \(\color{blue} \bullet\)), enter the population mean, \(\mu = 50\).

**Graphical Explanation:**

1. **75% Confidence Interval:**
   - A line is shown with markers from approximately 37.0 to 66.0, centering around a mean value for the sample (\(45.3\)), with a marker at 51.5 indicating the interval center.

2. **90% Confidence Interval:**
   - Similarly, a line shows values from approximately 37.0 to 66.0, with a marker at 51.5 for the interval center.

**(b)** Press the "Generate Samples" button to simulate taking 19 more samples of size \( n = 19 \) from the population. Notice that the confidence intervals for these samples are drawn automatically. Then complete parts (c) and (d) below the table.

**Table and Additional Graphs:**

The table shows sample means (\(S1\) to \(S20\)) and placeholders for confidence interval limits. The columns indicate:
- Each sample's mean
- The lower and upper limits for both 75% and 90% confidence intervals

**Graphical Explanation:**

- The left side shows a vertical array of the 75% confidence intervals for each sample.
- The right side shows a vertical array of the 90% confidence intervals.

The graphs demonstrate how each sample’s confidence interval is calculated and illustrates the distribution of sample means around the population mean (\( \
Transcribed Image Text:**Educational Text and Explanation of Graphs** You have taken a random sample of size \( n = 19 \) from a normal population that has a population mean of \( \mu = 50 \) and a population standard deviation of \( \sigma = 15 \). Your sample, which is Sample 1 in the table below, has a mean of \( \bar{x} = 45.3 \). ### Instructions: **(a)** Based on Sample 1, graph the 75% and 90% confidence intervals for the population mean. Use 1.150 for the critical value for the 75% confidence interval, and use 1.645 for the critical value for the 90% confidence interval. - Enter the lower and upper limits on the graphs to show each confidence interval. Write your answers with one decimal place. - For the points (\(\color{red} \bullet\) and \(\color{blue} \bullet\)), enter the population mean, \(\mu = 50\). **Graphical Explanation:** 1. **75% Confidence Interval:** - A line is shown with markers from approximately 37.0 to 66.0, centering around a mean value for the sample (\(45.3\)), with a marker at 51.5 indicating the interval center. 2. **90% Confidence Interval:** - Similarly, a line shows values from approximately 37.0 to 66.0, with a marker at 51.5 for the interval center. **(b)** Press the "Generate Samples" button to simulate taking 19 more samples of size \( n = 19 \) from the population. Notice that the confidence intervals for these samples are drawn automatically. Then complete parts (c) and (d) below the table. **Table and Additional Graphs:** The table shows sample means (\(S1\) to \(S20\)) and placeholders for confidence interval limits. The columns indicate: - Each sample's mean - The lower and upper limits for both 75% and 90% confidence intervals **Graphical Explanation:** - The left side shows a vertical array of the 75% confidence intervals for each sample. - The right side shows a vertical array of the 90% confidence intervals. The graphs demonstrate how each sample’s confidence interval is calculated and illustrates the distribution of sample means around the population mean (\( \
(c) Notice that for \( \frac{16}{20} = 80\% \) of the samples, the 90% confidence interval contains the population mean. Choose the correct statement.

- ○ When constructing 90% confidence intervals for 20 samples of the same size from the population, at most 90% of the samples will contain the population mean.
- ○ When constructing 90% confidence intervals for 20 samples of the same size from the population, exactly 90% of the samples must contain the population mean. There must have been an error with the way our samples were chosen.
- ○ When constructing 90% confidence intervals for 20 samples of the same size from the population, the percentage of the samples that contain the population mean should be close to 90%, but it may not be exactly 90%.

(d) Choose ALL that are true.

- □ The 75% confidence interval for Sample 15 indicates that 75% of the Sample 15 data values are between 44.4 and 52.4.
- □ From the 90% confidence interval for Sample 15, we cannot say that there is a 90% probability that the population mean is between 42.7 and 54.1.
- □ If there were a Sample 21 of size \( n = 38 \) taken from the same population as Sample 15, then the 90% confidence interval for Sample 21 would be narrower than the 90% confidence interval for Sample 15.
- □ The 75% confidence interval for Sample 15 is narrower than the 90% confidence interval for Sample 15. This is coincidence; when constructing a confidence interval for a sample, there is no relationship between the level of confidence and the width of the interval.
- □ None of the choices above are true.
Transcribed Image Text:(c) Notice that for \( \frac{16}{20} = 80\% \) of the samples, the 90% confidence interval contains the population mean. Choose the correct statement. - ○ When constructing 90% confidence intervals for 20 samples of the same size from the population, at most 90% of the samples will contain the population mean. - ○ When constructing 90% confidence intervals for 20 samples of the same size from the population, exactly 90% of the samples must contain the population mean. There must have been an error with the way our samples were chosen. - ○ When constructing 90% confidence intervals for 20 samples of the same size from the population, the percentage of the samples that contain the population mean should be close to 90%, but it may not be exactly 90%. (d) Choose ALL that are true. - □ The 75% confidence interval for Sample 15 indicates that 75% of the Sample 15 data values are between 44.4 and 52.4. - □ From the 90% confidence interval for Sample 15, we cannot say that there is a 90% probability that the population mean is between 42.7 and 54.1. - □ If there were a Sample 21 of size \( n = 38 \) taken from the same population as Sample 15, then the 90% confidence interval for Sample 21 would be narrower than the 90% confidence interval for Sample 15. - □ The 75% confidence interval for Sample 15 is narrower than the 90% confidence interval for Sample 15. This is coincidence; when constructing a confidence interval for a sample, there is no relationship between the level of confidence and the width of the interval. - □ None of the choices above are true.
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