Suppose x has a normal distribution with o = 1. A random sample of size 18 has a sample mean of x = 50.

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### Educational Exercise: Confidence Interval Calculation

**Problem Description:**

Suppose \( x \) has a normal distribution with \( \sigma = 1 \). A random sample of size 18 has a sample mean of \(\bar{x} = 50\).

#### (a) Conditions for Calculations

Identify the necessary conditions for the calculations:

- [ ] \( n \) is large
- [ ] Uniform distribution of \( x \)
- [x] \( \sigma \) is unknown
- [ ] \( \sigma \) is known

*Note: The correct conditions include a normal distribution of \( x \) and if \( \sigma \) is known or unknown.*

#### (b) Finding a 90% Confidence Interval for \(\mu\)

Calculate and input the following values, rounding to two decimal places:

- **Lower limit:** [ ]
- **Upper limit:** [ ]
- **Margin of error:** [ ]

*Note: Ensure calculations are precise as any errors would be indicated by a red cross.*

This exercise helps students understand the process of determining necessary conditions and calculating confidence intervals in statistics.
Transcribed Image Text:### Educational Exercise: Confidence Interval Calculation **Problem Description:** Suppose \( x \) has a normal distribution with \( \sigma = 1 \). A random sample of size 18 has a sample mean of \(\bar{x} = 50\). #### (a) Conditions for Calculations Identify the necessary conditions for the calculations: - [ ] \( n \) is large - [ ] Uniform distribution of \( x \) - [x] \( \sigma \) is unknown - [ ] \( \sigma \) is known *Note: The correct conditions include a normal distribution of \( x \) and if \( \sigma \) is known or unknown.* #### (b) Finding a 90% Confidence Interval for \(\mu\) Calculate and input the following values, rounding to two decimal places: - **Lower limit:** [ ] - **Upper limit:** [ ] - **Margin of error:** [ ] *Note: Ensure calculations are precise as any errors would be indicated by a red cross.* This exercise helps students understand the process of determining necessary conditions and calculating confidence intervals in statistics.
Sure! Here's the transcription and explanation:

---

**Title: Calculating Confidence Intervals for a Normal Distribution**

**Problem Statement:**
Suppose \( x \) has a normal distribution with \( \sigma = 11 \). A random sample of size 35 has a sample mean of \( \bar{x} = 70 \).

**(a) What conditions are necessary for your calculations? (Select all that apply.)**  
- [ ] uniform distribution of \( x \)  
- [ ] \( \sigma \) is unknown  
- [ ] \( n \) is large  
- [x] normal distribution of \( x \)  
- [x] \( \sigma \) is known  

**(b) Find a 95% confidence interval for \(\mu\). What is the margin of error? (Round your answers to two decimal places.)**  
*Note: Fill in the blanks based on your calculations.*
- Lower limit: [______]
- Upper limit: [______]
- Margin of error: [______]

---

**Explanation:**

In part (a), the necessary conditions for these calculations include having a normal distribution of \( x \) and knowing the population standard deviation \( \sigma \). These conditions allow the use of the Z-distribution to calculate the confidence interval.

In part (b), you are asked to find the 95% confidence interval for the population mean \(\mu\). The formula for the confidence interval is:
\[
\bar{x} \pm Z \left(\frac{\sigma}{\sqrt{n}}\right)
\]
With a 95% confidence level, the Z-value is typically 1.96. Calculate the margin of error and determine the lower and upper limits accordingly.
Transcribed Image Text:Sure! Here's the transcription and explanation: --- **Title: Calculating Confidence Intervals for a Normal Distribution** **Problem Statement:** Suppose \( x \) has a normal distribution with \( \sigma = 11 \). A random sample of size 35 has a sample mean of \( \bar{x} = 70 \). **(a) What conditions are necessary for your calculations? (Select all that apply.)** - [ ] uniform distribution of \( x \) - [ ] \( \sigma \) is unknown - [ ] \( n \) is large - [x] normal distribution of \( x \) - [x] \( \sigma \) is known **(b) Find a 95% confidence interval for \(\mu\). What is the margin of error? (Round your answers to two decimal places.)** *Note: Fill in the blanks based on your calculations.* - Lower limit: [______] - Upper limit: [______] - Margin of error: [______] --- **Explanation:** In part (a), the necessary conditions for these calculations include having a normal distribution of \( x \) and knowing the population standard deviation \( \sigma \). These conditions allow the use of the Z-distribution to calculate the confidence interval. In part (b), you are asked to find the 95% confidence interval for the population mean \(\mu\). The formula for the confidence interval is: \[ \bar{x} \pm Z \left(\frac{\sigma}{\sqrt{n}}\right) \] With a 95% confidence level, the Z-value is typically 1.96. Calculate the margin of error and determine the lower and upper limits accordingly.
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