The lengths of a particular animal's pregnancies are approximately normally distributed, with mean μ = 280 days and standard deviation o = 12 days. (a) What proportion of pregnancies lasts more than 295 days? (b) What proportion of pregnancies lasts between 274 and 286 days? (c) What is the probability that a randomly selected pregnancy lasts no more than 271 days? (d) A "ven protorm" habu in

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### Understanding the Distribution of Animal Pregnancy Lengths

The lengths of a particular animal's pregnancies are approximately normally distributed with a mean (μ) of 280 days and a standard deviation (σ) of 12 days. 

Here are the questions to explore:

1. **(a) What proportion of pregnancies lasts more than 295 days?**
   - **Solution Steps**: Calculate the Z-score for 295 days and use the standard normal distribution to find the proportion.

2. **(b) What proportion of pregnancies lasts between 274 and 286 days?**
   - **Solution Steps**: Calculate the Z-scores for 274 and 286 days and determine the area between these values on the standard normal distribution.

3. **(c) What is the probability that a randomly selected pregnancy lasts no more than 271 days?**
   - **Solution Steps**: Find the Z-score for 271 days and use it to determine the cumulative probability from the standard normal distribution.

4. **(d) A "very preterm" baby is one whose gestation period is less than 262 days. Are very preterm babies unusual?**
   - **Solution Steps**: Calculate the Z-score for 262 days. If the probability is low, such occurrences are considered unusual.

#### Interactive Learning
- **Table of Areas**: A table of areas under the normal curve can be accessed by clicking the icon. This table will help find exact probabilities by providing the areas corresponding to different Z-scores.

#### Problem Calculation
- **Example**: Determining Proportions

   - **(a)** The proportion of pregnancies that last more than 295 days can be calculated by first finding the Z-score:
     - Z = (X - μ) / σ = (295 - 280) / 12
     - Use the Z-score table to find the corresponding probability.

   - **Output**: (Results should be rounded to four decimal places.)

This structured exploration of normal distribution will help understand how gestational periods compare to standard statistical expectations. Use statistical tools or tables for precise calculations.
Transcribed Image Text:### Understanding the Distribution of Animal Pregnancy Lengths The lengths of a particular animal's pregnancies are approximately normally distributed with a mean (μ) of 280 days and a standard deviation (σ) of 12 days. Here are the questions to explore: 1. **(a) What proportion of pregnancies lasts more than 295 days?** - **Solution Steps**: Calculate the Z-score for 295 days and use the standard normal distribution to find the proportion. 2. **(b) What proportion of pregnancies lasts between 274 and 286 days?** - **Solution Steps**: Calculate the Z-scores for 274 and 286 days and determine the area between these values on the standard normal distribution. 3. **(c) What is the probability that a randomly selected pregnancy lasts no more than 271 days?** - **Solution Steps**: Find the Z-score for 271 days and use it to determine the cumulative probability from the standard normal distribution. 4. **(d) A "very preterm" baby is one whose gestation period is less than 262 days. Are very preterm babies unusual?** - **Solution Steps**: Calculate the Z-score for 262 days. If the probability is low, such occurrences are considered unusual. #### Interactive Learning - **Table of Areas**: A table of areas under the normal curve can be accessed by clicking the icon. This table will help find exact probabilities by providing the areas corresponding to different Z-scores. #### Problem Calculation - **Example**: Determining Proportions - **(a)** The proportion of pregnancies that last more than 295 days can be calculated by first finding the Z-score: - Z = (X - μ) / σ = (295 - 280) / 12 - Use the Z-score table to find the corresponding probability. - **Output**: (Results should be rounded to four decimal places.) This structured exploration of normal distribution will help understand how gestational periods compare to standard statistical expectations. Use statistical tools or tables for precise calculations.
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