Suppose the mean height in inches of all 9th grade students at one high school is estimated. The population standard deviation is 5 inches. The heights of 9 randomly selected students are 70, 69, 63, 73, 67, 65, 70, 63 and 73. Ex: 12.34 %3D Margin of error at 95% confidence level = Ex: 1.23 95% confidence interval = [ Ex: 12.34 Ex: 12.34 ] [smaller value, larger value]

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### Estimating the Mean Height of 9th Grade Students

To estimate the mean height of all 9th grade students at one high school, consider the following information and calculations.

**Given Data:**
- Population standard deviation (σ): 5 inches
- Heights of 9 randomly selected students (in inches): 70, 69, 63, 73, 67, 65, 70, 63, 73

**Sample Mean (\(\bar{x}\)):**
The sample mean height is calculated by taking the average of the heights of the 9 students.

\[ \bar{x} = \frac{(70 + 69 + 63 + 73 + 67 + 65 + 70 + 63 + 73)}{9} \approx 68.11 \text{ inches} \]

**Margin of Error at 95% Confidence Level:**
The margin of error (E) can be calculated using the formula for the confidence interval for a mean:

\[ E = z \left(\frac{\sigma}{\sqrt{n}}\right) \]

Where:
- \( z \) is the z-value corresponding to the 95% confidence level (approximately 1.96).
- \( \sigma \) is the population standard deviation (5 inches).
- \( n \) is the sample size (9).

\[ E = 1.96 \left(\frac{5}{\sqrt{9}}\right) = 1.96 \times \frac{5}{3} \approx 3.27 \text{ inches} \]

**95% Confidence Interval:**
The 95% confidence interval for the population mean is calculated as:

\[ CI = \left[ \bar{x} - E, \bar{x} + E \right] \]

Substituting the values:

\[ CI \approx \left[ 68.11 - 3.27, 68.11 + 3.27 \right] \]

\[ CI \approx \left[ 64.84, 71.38 \right] \]

**Summary:**
- Sample Mean (\(\bar{x}\)): ~68.11 inches
- Margin of Error (E) at 95% confidence level: ~3.27 inches
- 95% Confidence Interval: [64.84 inches, 71.38 inches]

This interval suggests that we are 95% confident that
Transcribed Image Text:### Estimating the Mean Height of 9th Grade Students To estimate the mean height of all 9th grade students at one high school, consider the following information and calculations. **Given Data:** - Population standard deviation (σ): 5 inches - Heights of 9 randomly selected students (in inches): 70, 69, 63, 73, 67, 65, 70, 63, 73 **Sample Mean (\(\bar{x}\)):** The sample mean height is calculated by taking the average of the heights of the 9 students. \[ \bar{x} = \frac{(70 + 69 + 63 + 73 + 67 + 65 + 70 + 63 + 73)}{9} \approx 68.11 \text{ inches} \] **Margin of Error at 95% Confidence Level:** The margin of error (E) can be calculated using the formula for the confidence interval for a mean: \[ E = z \left(\frac{\sigma}{\sqrt{n}}\right) \] Where: - \( z \) is the z-value corresponding to the 95% confidence level (approximately 1.96). - \( \sigma \) is the population standard deviation (5 inches). - \( n \) is the sample size (9). \[ E = 1.96 \left(\frac{5}{\sqrt{9}}\right) = 1.96 \times \frac{5}{3} \approx 3.27 \text{ inches} \] **95% Confidence Interval:** The 95% confidence interval for the population mean is calculated as: \[ CI = \left[ \bar{x} - E, \bar{x} + E \right] \] Substituting the values: \[ CI \approx \left[ 68.11 - 3.27, 68.11 + 3.27 \right] \] \[ CI \approx \left[ 64.84, 71.38 \right] \] **Summary:** - Sample Mean (\(\bar{x}\)): ~68.11 inches - Margin of Error (E) at 95% confidence level: ~3.27 inches - 95% Confidence Interval: [64.84 inches, 71.38 inches] This interval suggests that we are 95% confident that
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