The mean and standard deviation of a random sample of n measurements are equal to 34.9 and 3.7, respectively. a. Find a 99% confidence interval for u if n = 121. b. Find a 99% confidence interval for u ifn=484. c. Find the widths of the confidence intervals found in parts a and b. What is the effect on the width of a confidence interval of quadrupling the sample size while holding the confidence coefficient fixed?
The mean and standard deviation of a random sample of n measurements are equal to 34.9 and 3.7, respectively. a. Find a 99% confidence interval for u if n = 121. b. Find a 99% confidence interval for u ifn=484. c. Find the widths of the confidence intervals found in parts a and b. What is the effect on the width of a confidence interval of quadrupling the sample size while holding the confidence coefficient fixed?
MATLAB: An Introduction with Applications
6th Edition
ISBN:9781119256830
Author:Amos Gilat
Publisher:Amos Gilat
Chapter1: Starting With Matlab
Section: Chapter Questions
Problem 1P
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![### Confidence Intervals and Sample Size
The mean and standard deviation of a random sample of \( n \) measurements are equal to 34.9 and 3.7, respectively.
**a. Find a 99% confidence interval for \( \mu \) if \( n = 121 \).**
**b. Find a 99% confidence interval for \( \mu \) if \( n = 484 \).**
**c. Find the widths of the confidence intervals found in parts a and b. What is the effect on the width of a confidence interval of quadrupling the sample size while holding the confidence coefficient fixed?**
### Explanation of Concepts
#### Confidence Interval
A confidence interval is a range of values, derived from sample statistics, that is likely to contain the value of an unknown population parameter. The 99% confidence interval means we are 99% certain that the true population mean lies within this interval.
#### Effect of Sample Size
Increasing the sample size generally results in a narrower confidence interval, assuming the level of confidence remains the same. This is because larger samples tend to give more reliable estimates of the population parameter.
### Detailed Steps to Solve
1. **Identify the given values:**
- Sample mean (\( \bar{x} \)) = 34.9
- Standard deviation (\( s \)) = 3.7
2. **Determine the confidence level:**
- 99% confidence level
3. **Find the critical value (\( Z_{\alpha/2} \)) corresponding to the 99% confidence level using standard normal (Z) distribution.**
4. **Calculate the standard error of the mean:**
\[
SE = \frac{s}{\sqrt{n}}
\]
5. **Determine the margin of error:**
\[
Margin\ of\ Error = Z_{\alpha/2} \times SE
\]
6. **Construct the confidence interval:**
\[
CI = \bar{x} \pm Margin\ of\ Error
\]
#### For part a: \( n = 121 \)
#### For part b: \( n = 484 \)
#### For part c: Compare the widths of the intervals found in parts a and b. Analyze the effect of increasing the sample size.
By following these steps and calculations, you can understand how sample size affects the width of the confidence interval while maintaining the same confidence](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fd210f98b-1208-4eea-a54e-043fbbd49724%2F4e9426a1-9d45-42ef-a201-5a895684fec4%2Fj9b42kg.png&w=3840&q=75)
Transcribed Image Text:### Confidence Intervals and Sample Size
The mean and standard deviation of a random sample of \( n \) measurements are equal to 34.9 and 3.7, respectively.
**a. Find a 99% confidence interval for \( \mu \) if \( n = 121 \).**
**b. Find a 99% confidence interval for \( \mu \) if \( n = 484 \).**
**c. Find the widths of the confidence intervals found in parts a and b. What is the effect on the width of a confidence interval of quadrupling the sample size while holding the confidence coefficient fixed?**
### Explanation of Concepts
#### Confidence Interval
A confidence interval is a range of values, derived from sample statistics, that is likely to contain the value of an unknown population parameter. The 99% confidence interval means we are 99% certain that the true population mean lies within this interval.
#### Effect of Sample Size
Increasing the sample size generally results in a narrower confidence interval, assuming the level of confidence remains the same. This is because larger samples tend to give more reliable estimates of the population parameter.
### Detailed Steps to Solve
1. **Identify the given values:**
- Sample mean (\( \bar{x} \)) = 34.9
- Standard deviation (\( s \)) = 3.7
2. **Determine the confidence level:**
- 99% confidence level
3. **Find the critical value (\( Z_{\alpha/2} \)) corresponding to the 99% confidence level using standard normal (Z) distribution.**
4. **Calculate the standard error of the mean:**
\[
SE = \frac{s}{\sqrt{n}}
\]
5. **Determine the margin of error:**
\[
Margin\ of\ Error = Z_{\alpha/2} \times SE
\]
6. **Construct the confidence interval:**
\[
CI = \bar{x} \pm Margin\ of\ Error
\]
#### For part a: \( n = 121 \)
#### For part b: \( n = 484 \)
#### For part c: Compare the widths of the intervals found in parts a and b. Analyze the effect of increasing the sample size.
By following these steps and calculations, you can understand how sample size affects the width of the confidence interval while maintaining the same confidence
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