Construct a 95% confidence interval for the population mean, μ. Assume the population has a normal distribution. A sample of 20 college students had mean annual earnings of $3120 with a standard deviation of $677. contents OA. ($1324,$1567) B. ($2657,$2891) C. ($2803,$3437) D. ($2135,$2567) e Resourc r Success or Success media Library F estly cloudy Ask my instructor H 4 Clear all Check answer

A First Course in Probability (10th Edition)
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### Constructing a 95% Confidence Interval for Population Mean

**Scenario:**
You are given a task to construct a 95% confidence interval for the population mean, denoted as \( \mu \). Assume the population follows a normal distribution. A sample of 20 college students yields the following statistics:
- Mean annual earnings: $3120
- Standard deviation: $677

**Options:**
You are provided with four potential confidence intervals. Select the correct one:
- A. ($1324, $1567)
- B. ($2657, $2991)
- C. ($2803, $3437)
- D. ($2135, $2567)

**Steps to Solve:**
1. **Identify Given Information:**
   - Sample size (n): 20
   - Sample mean (\( \bar{x} \)): $3120
   - Sample standard deviation (s): $677

2. **Determine the Confidence Level:**
   Since the confidence level is 95%, the corresponding z-value (critical value) for a two-tailed test is approximately 1.96 (from z-tables).

3. **Calculate the Margin of Error (ME):**
   The formula for the margin of error in this context is given by:

   \[ ME = z \times \left(\frac{s}{\sqrt{n}}\right) \]

4. **Substitute Given Values into Formula:**
   \[
   ME = 1.96 \times \left(\frac{677}{\sqrt{20}}\right)
   \]

5. **Compute Margin of Error:**
   \[
   ME = 1.96 \times \left(\frac{677}{4.47}\right) \approx 1.96 \times 151.45 \approx 296.84
   \]

6. **Determine the Confidence Interval:**
   The confidence interval can be found using:

    \[
    \left( \bar{x} - ME, \bar{x} + ME \right)
    \]

7. **Substitute Values:**
   \[
   \left( 3120 - 296.84, 3120 + 296.84 \right) \approx \left( 2823.16, 3416.84 \right)
   \]

Therefore, the correct answer from the options given is:
- C. ($2803
Transcribed Image Text:### Constructing a 95% Confidence Interval for Population Mean **Scenario:** You are given a task to construct a 95% confidence interval for the population mean, denoted as \( \mu \). Assume the population follows a normal distribution. A sample of 20 college students yields the following statistics: - Mean annual earnings: $3120 - Standard deviation: $677 **Options:** You are provided with four potential confidence intervals. Select the correct one: - A. ($1324, $1567) - B. ($2657, $2991) - C. ($2803, $3437) - D. ($2135, $2567) **Steps to Solve:** 1. **Identify Given Information:** - Sample size (n): 20 - Sample mean (\( \bar{x} \)): $3120 - Sample standard deviation (s): $677 2. **Determine the Confidence Level:** Since the confidence level is 95%, the corresponding z-value (critical value) for a two-tailed test is approximately 1.96 (from z-tables). 3. **Calculate the Margin of Error (ME):** The formula for the margin of error in this context is given by: \[ ME = z \times \left(\frac{s}{\sqrt{n}}\right) \] 4. **Substitute Given Values into Formula:** \[ ME = 1.96 \times \left(\frac{677}{\sqrt{20}}\right) \] 5. **Compute Margin of Error:** \[ ME = 1.96 \times \left(\frac{677}{4.47}\right) \approx 1.96 \times 151.45 \approx 296.84 \] 6. **Determine the Confidence Interval:** The confidence interval can be found using: \[ \left( \bar{x} - ME, \bar{x} + ME \right) \] 7. **Substitute Values:** \[ \left( 3120 - 296.84, 3120 + 296.84 \right) \approx \left( 2823.16, 3416.84 \right) \] Therefore, the correct answer from the options given is: - C. ($2803
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