You measure 20 randomly selected textbooks' weights, and find they have a mean weight of 37 ounces. Assume the population standard deviation is 8.1 ounces. Based on this, construct a 99% confidence interval for the true population mean textbook weight. Give your answers as decimals, to two places

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### Calculating a 99% Confidence Interval for Textbook Weights

**Given Data:**
- **Sample Size (n):** 20 textbooks
- **Sample Mean (\(\bar{x}\)):** 37 ounces
- **Population Standard Deviation (\(\sigma\)):** 8.1 ounces

### Objective
We aim to construct a 99% confidence interval for the true mean weight (\(\mu\)) of textbooks.

### Steps to Calculate the Confidence Interval:

1. **Determine the Z-score for 99% Confidence Level:**
   For a 99% confidence level, the Z-score is approximately 2.576 (from standard Z-tables).

2. **Calculate the Standard Error of the Mean (SEM):**
   
   \[
   \text{SEM} = \frac{\sigma}{\sqrt{n}} = \frac{8.1}{\sqrt{20}}
   \]
   
3. **Calculate the Margin of Error (ME):**
   
   \[
   \text{ME} = Z \times \text{SEM} = 2.576 \times \frac{8.1}{\sqrt{20}}
   \]
   
4. **Compute the Confidence Interval:**
   
   \[
   \text{Lower Limit} = \bar{x} - \text{ME}
   \]
   \[
   \text{Upper Limit} = \bar{x} + \text{ME}
   \]

### Final Confidence Interval:
   
Given the steps above, you can plug in the values to get the confidence interval.

### Answer Format:
Enter your answers as decimals rounded to two places.

\[
\boxed{\text{Lower Limit}} < \mu < \boxed{\text{Upper Limit}}
\]

Ensure your answer boxes are filled accordingly with your final results.
Transcribed Image Text:### Calculating a 99% Confidence Interval for Textbook Weights **Given Data:** - **Sample Size (n):** 20 textbooks - **Sample Mean (\(\bar{x}\)):** 37 ounces - **Population Standard Deviation (\(\sigma\)):** 8.1 ounces ### Objective We aim to construct a 99% confidence interval for the true mean weight (\(\mu\)) of textbooks. ### Steps to Calculate the Confidence Interval: 1. **Determine the Z-score for 99% Confidence Level:** For a 99% confidence level, the Z-score is approximately 2.576 (from standard Z-tables). 2. **Calculate the Standard Error of the Mean (SEM):** \[ \text{SEM} = \frac{\sigma}{\sqrt{n}} = \frac{8.1}{\sqrt{20}} \] 3. **Calculate the Margin of Error (ME):** \[ \text{ME} = Z \times \text{SEM} = 2.576 \times \frac{8.1}{\sqrt{20}} \] 4. **Compute the Confidence Interval:** \[ \text{Lower Limit} = \bar{x} - \text{ME} \] \[ \text{Upper Limit} = \bar{x} + \text{ME} \] ### Final Confidence Interval: Given the steps above, you can plug in the values to get the confidence interval. ### Answer Format: Enter your answers as decimals rounded to two places. \[ \boxed{\text{Lower Limit}} < \mu < \boxed{\text{Upper Limit}} \] Ensure your answer boxes are filled accordingly with your final results.
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