Insurance companies are interested in knowing the population percent of drivers who always buckle up before riding in a car. They randomly survey 381 drivers and find that 320 claim to always buckle up. Construct a 95% confidence interval for the population proportion that claim to always buckle up.

MATLAB: An Introduction with Applications
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ISBN:9781119256830
Author:Amos Gilat
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**Educational Content: Understanding Confidence Intervals**

Insurance companies are interested in knowing the percentage of drivers who always buckle up before riding in a car. They randomly survey 381 drivers and find that 320 claim to always buckle up.

**Objective:**
Construct a 95% confidence interval for the population proportion that claims to always buckle up.

**Instructions:**
- Use the sample data to determine the population proportion confidence interval.
- Do not round intermediate steps; round the final answer to four decimal places.

**Step-by-Step Guide:**

1. **Identify the Sample Proportion (\(\hat{p}\)):**
   - Calculate \( \hat{p} = \frac{320}{381} \).
  
2. **Determine the Standard Error (SE):**
   - Use the formula for the standard error of a proportion:
     \[
     \text{SE} = \sqrt{\frac{\hat{p}(1-\hat{p})}{n}}
     \]

3. **Find the Z-score for 95% Confidence Level:**
   - Typically, the Z-score is 1.96 for a 95% confidence interval.

4. **Calculate the Confidence Interval:**
   - Use the formula:
     \[
     \hat{p} \pm Z \times \text{SE}
     \]

5. **Conclusion:**
   - Interpreting the results, the confidence interval provides a range that is likely to contain the true population proportion of drivers who always buckle up with a 95% level of certainty.

This process helps understand how statistical confidence intervals are used to make inferences about a population based on a sample.
Transcribed Image Text:**Educational Content: Understanding Confidence Intervals** Insurance companies are interested in knowing the percentage of drivers who always buckle up before riding in a car. They randomly survey 381 drivers and find that 320 claim to always buckle up. **Objective:** Construct a 95% confidence interval for the population proportion that claims to always buckle up. **Instructions:** - Use the sample data to determine the population proportion confidence interval. - Do not round intermediate steps; round the final answer to four decimal places. **Step-by-Step Guide:** 1. **Identify the Sample Proportion (\(\hat{p}\)):** - Calculate \( \hat{p} = \frac{320}{381} \). 2. **Determine the Standard Error (SE):** - Use the formula for the standard error of a proportion: \[ \text{SE} = \sqrt{\frac{\hat{p}(1-\hat{p})}{n}} \] 3. **Find the Z-score for 95% Confidence Level:** - Typically, the Z-score is 1.96 for a 95% confidence interval. 4. **Calculate the Confidence Interval:** - Use the formula: \[ \hat{p} \pm Z \times \text{SE} \] 5. **Conclusion:** - Interpreting the results, the confidence interval provides a range that is likely to contain the true population proportion of drivers who always buckle up with a 95% level of certainty. This process helps understand how statistical confidence intervals are used to make inferences about a population based on a sample.
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