A random sample of 92 observations produced a mean x = 25.8 and a standard deviation s = 2.4. a. Find a 95% confidence interval for µ. b. Find a 90% confidence interval for µ. c. Find a 99% confidence interval for u.

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### Confidence Interval Calculations

A random sample of 92 observations produced a mean (x̄) of 25.8 and a standard deviation (s) of 2.4.

#### Tasks:
a. Find a 95% confidence interval for μ.  
b. Find a 90% confidence interval for μ.  
c. Find a 99% confidence interval for μ.  

### Step-by-Step Solution:

**1. Identify the parameters:**
- Sample mean (x̄) = 25.8
- Sample standard deviation (s) = 2.4
- Sample size (n) = 92

**2. Calculate the standard error of the mean (SEM):**
\[ \text{SEM} = \frac{s}{\sqrt{n}} = \frac{2.4}{\sqrt{92}} \]

**3. Use the appropriate z-score for each confidence level:**
- For a 95% confidence interval, the z-score is approximately 1.96.
- For a 90% confidence interval, the z-score is approximately 1.645.
- For a 99% confidence interval, the z-score is approximately 2.576.

**4. Calculate the margin of error (ME):**
\[ \text{ME} = z \times \text{SEM} \]

**5. Construct the confidence intervals:**

\[ \text{Confidence Interval} = x̄ \pm \text{ME} \]

**a. 95% Confidence Interval:**
- Calculate SEM:
\[ \text{SEM} = \frac{2.4}{\sqrt{92}} \approx 0.25 \]
- Calculate ME:
\[ \text{ME} = 1.96 \times 0.25 \approx 0.49 \]
- Confidence Interval:
\[ 25.8 \pm 0.49 = (25.31, 26.29) \]

**b. 90% Confidence Interval:**
- Calculate ME:
\[ \text{ME} = 1.645 \times 0.25 \approx 0.41 \]
- Confidence Interval:
\[ 25.8 \pm 0.41 = (25.39, 26.21) \]

**c. 99% Confidence Interval:**
- Calculate ME:
\[ \text{ME} = 2.576 \times 0
Transcribed Image Text:### Confidence Interval Calculations A random sample of 92 observations produced a mean (x̄) of 25.8 and a standard deviation (s) of 2.4. #### Tasks: a. Find a 95% confidence interval for μ. b. Find a 90% confidence interval for μ. c. Find a 99% confidence interval for μ. ### Step-by-Step Solution: **1. Identify the parameters:** - Sample mean (x̄) = 25.8 - Sample standard deviation (s) = 2.4 - Sample size (n) = 92 **2. Calculate the standard error of the mean (SEM):** \[ \text{SEM} = \frac{s}{\sqrt{n}} = \frac{2.4}{\sqrt{92}} \] **3. Use the appropriate z-score for each confidence level:** - For a 95% confidence interval, the z-score is approximately 1.96. - For a 90% confidence interval, the z-score is approximately 1.645. - For a 99% confidence interval, the z-score is approximately 2.576. **4. Calculate the margin of error (ME):** \[ \text{ME} = z \times \text{SEM} \] **5. Construct the confidence intervals:** \[ \text{Confidence Interval} = x̄ \pm \text{ME} \] **a. 95% Confidence Interval:** - Calculate SEM: \[ \text{SEM} = \frac{2.4}{\sqrt{92}} \approx 0.25 \] - Calculate ME: \[ \text{ME} = 1.96 \times 0.25 \approx 0.49 \] - Confidence Interval: \[ 25.8 \pm 0.49 = (25.31, 26.29) \] **b. 90% Confidence Interval:** - Calculate ME: \[ \text{ME} = 1.645 \times 0.25 \approx 0.41 \] - Confidence Interval: \[ 25.8 \pm 0.41 = (25.39, 26.21) \] **c. 99% Confidence Interval:** - Calculate ME: \[ \text{ME} = 2.576 \times 0
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