A simple random sample from a population with a normal distribution of 104 body temperatures has x= 98.20°F and s = 0.69°F. Construct a 95% confidence interval estimate of the standard deviation of body temperature of all healthy humans. Click the icon to view the table of Chi-Square critical values. D°F

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### Confidence Interval Estimate for Standard Deviation

**Problem Statement:**

A simple random sample from a population with a normal distribution includes 104 body temperatures. The sample mean is \( \bar{x} = 98.20^\circ F \) and the sample standard deviation is \( s = 0.69^\circ F \). Construct a 95% confidence interval estimate of the standard deviation of body temperature for all healthy humans.

**Instructions:**

Click the icon to view the table of Chi-Square critical values.

**Confidence Interval Formula:**

To calculate the confidence interval for the standard deviation, use the formula based on the Chi-Square distribution:

1. The formula to estimate the confidence interval for the variance is given by:

   \[
   \frac{(n-1)s^2}{\chi^2_{\alpha/2}} < \sigma^2 < \frac{(n-1)s^2}{\chi^2_{1-\alpha/2}}
   \]

2. To find the confidence interval for the standard deviation, take the square root of the variance interval:

   \[
   \sqrt{\frac{(n-1)s^2}{\chi^2_{\alpha/2}}} < \sigma < \sqrt{\frac{(n-1)s^2}{\chi^2_{1-\alpha/2}}}
   \]

**Calculation:**

1. Determine the degrees of freedom: \( n-1 = 103 \)
2. Look up the Chi-Square critical values corresponding to \(\alpha/2\) and \(1-\alpha/2\) for 95% confidence and 103 degrees of freedom.
3. Substitute the values into the formula to find the lower and upper bounds of the confidence interval for the standard deviation.
4. Round the results to two decimal places.

**Result:**

- \(__^\circ F < \sigma < __^\circ F\)

(Round to two decimal places as needed.)

**Note:**

Ensure to refer to a Chi-Square distribution table or calculator for accurate critical values needed for the calculation.
Transcribed Image Text:### Confidence Interval Estimate for Standard Deviation **Problem Statement:** A simple random sample from a population with a normal distribution includes 104 body temperatures. The sample mean is \( \bar{x} = 98.20^\circ F \) and the sample standard deviation is \( s = 0.69^\circ F \). Construct a 95% confidence interval estimate of the standard deviation of body temperature for all healthy humans. **Instructions:** Click the icon to view the table of Chi-Square critical values. **Confidence Interval Formula:** To calculate the confidence interval for the standard deviation, use the formula based on the Chi-Square distribution: 1. The formula to estimate the confidence interval for the variance is given by: \[ \frac{(n-1)s^2}{\chi^2_{\alpha/2}} < \sigma^2 < \frac{(n-1)s^2}{\chi^2_{1-\alpha/2}} \] 2. To find the confidence interval for the standard deviation, take the square root of the variance interval: \[ \sqrt{\frac{(n-1)s^2}{\chi^2_{\alpha/2}}} < \sigma < \sqrt{\frac{(n-1)s^2}{\chi^2_{1-\alpha/2}}} \] **Calculation:** 1. Determine the degrees of freedom: \( n-1 = 103 \) 2. Look up the Chi-Square critical values corresponding to \(\alpha/2\) and \(1-\alpha/2\) for 95% confidence and 103 degrees of freedom. 3. Substitute the values into the formula to find the lower and upper bounds of the confidence interval for the standard deviation. 4. Round the results to two decimal places. **Result:** - \(__^\circ F < \sigma < __^\circ F\) (Round to two decimal places as needed.) **Note:** Ensure to refer to a Chi-Square distribution table or calculator for accurate critical values needed for the calculation.
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