d. n= 90, x = 4.91 e. Is the assumption that the underlying population of measurements is normally distributed necessary to ensure the validity of the confidence intervals in parts a through d? Explain. a. ( 30.511, 37.489 ) (Round to two decimal places as needed.) b. (113.985, 118.015 ) (Round to two decimal places as needed.) c. ( 12.399 , 17.601) (Round to two decihal places as needed.) d. (Round to two decimal places as needed.)

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### Confidence Intervals Calculation

A random sample of \( n \) measurements was selected from a population with an unknown mean \( \mu \) and standard deviation \( \sigma = 15 \). For each of the given situations (a through d), calculate a 90% confidence interval for \( \mu \).

#### Given Data:
- **a.** \( n = 50, \overline{x} = 34 \)
- **b.** \( n = 150, \overline{x} = 116 \)
- **c.** \( n = 90, \overline{x} = 15 \)
- **d.** \( n = 90, \overline{x} = 4.91 \)

#### Calculated 90% Confidence Intervals:
- **a.** \( (30.511, 37.489) \)
  - *Rounded to two decimal places as needed:*
  - \( (30.51, 37.49) \)

- **b.** \( (113.985, 118.015) \)
  - *Rounded to two decimal places as needed:*
  - \( (113.99, 118.02) \)

- **c.** \( (12.399, 17.601) \)
  - *Rounded to two decimal places as needed:*
  - \( (12.40, 17.60) \)

- **d.** 
  - *Parts of the interval are left blank; please ensure to complete the calculations as necessary.*
  - \( (?, ?) \)

#### Additional Question:
- **e. Is the assumption that the underlying population of measurements is normally distributed necessary to ensure the validity of the confidence intervals in parts a through d? Explain.**

### Explanation of Calculation Method:
To calculate a 90% confidence interval for the population mean \( \mu \) when the population standard deviation \( \sigma \) is known, the following formula is used:

\[ \overline{x} \pm Z \left(\frac{\sigma}{\sqrt{n}}\right) \]

Where:
- \( \overline{x} \) is the sample mean.
- \( \sigma \) is the population standard deviation.
- \( n \) is the sample size.
- \( Z \) is the Z-score corresponding to the desired confidence level (for 90%, \( Z \approx
Transcribed Image Text:### Confidence Intervals Calculation A random sample of \( n \) measurements was selected from a population with an unknown mean \( \mu \) and standard deviation \( \sigma = 15 \). For each of the given situations (a through d), calculate a 90% confidence interval for \( \mu \). #### Given Data: - **a.** \( n = 50, \overline{x} = 34 \) - **b.** \( n = 150, \overline{x} = 116 \) - **c.** \( n = 90, \overline{x} = 15 \) - **d.** \( n = 90, \overline{x} = 4.91 \) #### Calculated 90% Confidence Intervals: - **a.** \( (30.511, 37.489) \) - *Rounded to two decimal places as needed:* - \( (30.51, 37.49) \) - **b.** \( (113.985, 118.015) \) - *Rounded to two decimal places as needed:* - \( (113.99, 118.02) \) - **c.** \( (12.399, 17.601) \) - *Rounded to two decimal places as needed:* - \( (12.40, 17.60) \) - **d.** - *Parts of the interval are left blank; please ensure to complete the calculations as necessary.* - \( (?, ?) \) #### Additional Question: - **e. Is the assumption that the underlying population of measurements is normally distributed necessary to ensure the validity of the confidence intervals in parts a through d? Explain.** ### Explanation of Calculation Method: To calculate a 90% confidence interval for the population mean \( \mu \) when the population standard deviation \( \sigma \) is known, the following formula is used: \[ \overline{x} \pm Z \left(\frac{\sigma}{\sqrt{n}}\right) \] Where: - \( \overline{x} \) is the sample mean. - \( \sigma \) is the population standard deviation. - \( n \) is the sample size. - \( Z \) is the Z-score corresponding to the desired confidence level (for 90%, \( Z \approx
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