there is a 5k race, the recorded time was normally distributed with a mean time of 28 and a standard deviation of 5 minutes. it is a known that 20% of the
there is a 5k race, the recorded time was normally distributed with a mean time of 28 and a standard deviation of 5 minutes. it is a known that 20% of the
Calculus For The Life Sciences
2nd Edition
ISBN:9780321964038
Author:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Publisher:GREENWELL, Raymond N., RITCHEY, Nathan P., Lial, Margaret L.
Chapter13: Probability And Calculus
Section13.3: Special Probability Density Functions
Problem 7E
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![### Understanding Normal Distribution in 5K Race Times
In a study of a 5K race, the time taken to complete the race was found to be normally distributed. The key statistical measures are:
- **Mean Time:** 28 minutes
- **Standard Deviation:** 5 minutes
From the data, it is known that:
- 20% of the runners took more than 28 minutes but less than \( k \) minutes to complete the race.
### Problem Statement
We need to determine the value of \( k \) using the principles of normal distribution.
### Solution Approach
1. **Identify the Mean and Standard Deviation:**
- Mean (\( \mu \)) = 28 minutes
- Standard Deviation (\( \sigma \)) = 5 minutes
2. **Understand the Normal Distribution:**
- The normal distribution is symmetric about the mean.
- The area under the curve represents the probability.
3. **Calculate the Z-Score:**
- The Z-score represents the number of standard deviations a data point is from the mean.
- \( Z = \frac{X - \mu}{\sigma} \)
4. **Use the Given Probabilities:**
- 20% of the runners took more than 28 minutes but less than \( k \) minutes. This implies that the area under the normal curve from a Z-score of 0 to the Z-score corresponding to \( k \) is 0.20.
5. **Find the Corresponding Z-Score:**
- Using a Z-table or normal distribution calculator, find the Z-score for which 20% of the distribution lies between 0 and Z. This Z-score corresponds to the upper 20% of the mean.
- Let Z be the Z-score such that \( P(0 < Z < z) = 0.20 \).
6. **Calculate \( k \):**
- \( k = \mu + Z \sigma \)
- Substitute \( \mu \), \( \sigma \), and the Z value obtained from the table.
7. **Interpret the Value:**
- \( k \) will be the time in minutes.
By applying these steps, you should be able to determine the value of \( k \) according to the normal distribution laws.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2Fc09b8323-23e8-423b-9399-551540e09fa1%2F1f691bc2-8c9a-459d-ae70-4878e56edf13%2Frbf1g2y_processed.jpeg&w=3840&q=75)
Transcribed Image Text:### Understanding Normal Distribution in 5K Race Times
In a study of a 5K race, the time taken to complete the race was found to be normally distributed. The key statistical measures are:
- **Mean Time:** 28 minutes
- **Standard Deviation:** 5 minutes
From the data, it is known that:
- 20% of the runners took more than 28 minutes but less than \( k \) minutes to complete the race.
### Problem Statement
We need to determine the value of \( k \) using the principles of normal distribution.
### Solution Approach
1. **Identify the Mean and Standard Deviation:**
- Mean (\( \mu \)) = 28 minutes
- Standard Deviation (\( \sigma \)) = 5 minutes
2. **Understand the Normal Distribution:**
- The normal distribution is symmetric about the mean.
- The area under the curve represents the probability.
3. **Calculate the Z-Score:**
- The Z-score represents the number of standard deviations a data point is from the mean.
- \( Z = \frac{X - \mu}{\sigma} \)
4. **Use the Given Probabilities:**
- 20% of the runners took more than 28 minutes but less than \( k \) minutes. This implies that the area under the normal curve from a Z-score of 0 to the Z-score corresponding to \( k \) is 0.20.
5. **Find the Corresponding Z-Score:**
- Using a Z-table or normal distribution calculator, find the Z-score for which 20% of the distribution lies between 0 and Z. This Z-score corresponds to the upper 20% of the mean.
- Let Z be the Z-score such that \( P(0 < Z < z) = 0.20 \).
6. **Calculate \( k \):**
- \( k = \mu + Z \sigma \)
- Substitute \( \mu \), \( \sigma \), and the Z value obtained from the table.
7. **Interpret the Value:**
- \( k \) will be the time in minutes.
By applying these steps, you should be able to determine the value of \( k \) according to the normal distribution laws.
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