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A county official would like to estimate the proportion of homes in their county that were heated by natural gas. They randomly select 1200 homes in their county and find that \( 45 \% \) were heated by natural gas. Construct a \( 95 \% \) confidence interval for the population proportion of of homes in their county that were heated by natural gas. Do not round between steps. Round answers to at least 4 decimal places. Select an answer \( \hat{v}<\square \)

Ask by Norton Griffiths. in the United States
Feb 25,2025

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Answer

The 95% confidence interval for the proportion of homes heated by natural gas is (0.4218, 0.4782).

Solution

Step 1. Identify the sample proportion. • ẑ = 0.45 (since 45% of 1200 homes were heated by natural gas). Step 2. Calculate the standard error (SE) for the proportion. • SE = √[ẑ(1 - ẑ) / n] = √[0.45 × 0.55 / 1200] • = √(0.2475 / 1200) • = √(0.00020625) • ≈ 0.0144 Step 3. Determine the critical z-value for a 95% confidence interval. • For 95% confidence, the critical z-value is approximately 1.96. Step 4. Compute the margin of error (ME). • ME = z* × SE = 1.96 × 0.0144 ≈ 0.0282 Step 5. Construct the 95% confidence interval. • Lower limit = 0.45 − 0.0282 = 0.4218 • Upper limit = 0.45 + 0.0282 = 0.4782 Rounded to four decimal places, the 95% confidence interval for the population proportion is approximately:   (0.4218, 0.4782). Thus, the answer is: 0.4218 < p < 0.4782.

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To construct a \( 95\% \) confidence interval for the population proportion of homes heated by natural gas, we first need to calculate the sample proportion (\( \hat{p} \)) and the standard error (SE). 1. Sample proportion \( \hat{p} = 0.45 \) (i.e., \( 45\% \) of \( 1200 \)). 2. Standard error (SE) is calculated using the formula: \[ SE = \sqrt{\frac{\hat{p}(1 - \hat{p})}{n}} \] where \( n = 1200 \): \[ SE = \sqrt{\frac{0.45 \times 0.55}{1200}} \approx \sqrt{\frac{0.2475}{1200}} \approx \sqrt{0.00020625} \approx 0.0144 \] 3. For a \( 95\% \) confidence interval, we use a \( z \)-value of approximately \( 1.96 \). 4. Margin of error (ME) is calculated as: \[ ME = z \times SE = 1.96 \times 0.0144 \approx 0.028224 \] 5. The confidence interval is: \[ \hat{p} \pm ME = 0.45 \pm 0.028224 \] Finally, calculating the interval: - Lower limit: \( 0.45 - 0.028224 \approx 0.4218 \) - Upper limit: \( 0.45 + 0.028224 \approx 0.4782 \) Thus, the \( 95\% \) confidence interval for the proportion of homes heated by natural gas is approximately \( (0.4218, 0.4782) \). Select an answer \( \hat{v}<0.4782 \)

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