(g) What is the cutoff number of days for a pregnancy for the bottom 20% of women?

MATLAB: An Introduction with Applications
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Question G

### Understanding Pregnancy Duration and Probability

The lengths of pregnancies are normally distributed with a mean of 280 days and a standard deviation of 16 days. The following problems help us explore probabilities related to the length of pregnancies.

#### Questions:

(a) **Probability of Shorter Pregnancy:**
   - Find the probability that an individual woman has a pregnancy shorter than 271 days.

(b) **Probability for a Sample Mean:**
   - If 25 women are randomly selected, find the probability that they have a mean pregnancy shorter than 271 days.

(c) **Methodological Differences:**
   - There should be a difference in your method for the previous two questions. Explain what you did differently for each problem and explain WHY your answers are different.

(d) **Probability of Longer Pregnancy:**
   - Find the probability that an individual woman has a pregnancy longer than 300 days.

(e) **Probability of Pregnancy Between Two Values:**
   - Find the probability that an individual woman has a pregnancy between 280 and 300 days.

(f) **Cutoff for the Top 15%:**
   - What is the cutoff number of days for a pregnancy for the top 15% of women?

(g) **Cutoff for the Bottom 20%:**
   - What is the cutoff number of days for a pregnancy for the bottom 20% of women?

#### Explanation of Approaches:

- **Calculating Probabilities for Individuals vs. Samples:**
  - For individual probabilities (questions a and d), use the standard normal distribution with the given mean and standard deviation.
  - For sample means (question b), use the standard error to adjust the standard deviation, as the sample size affects variability.

- **Interpreting Results:**
  - Understanding how the probabilities reflect population characteristics helps in statistical reasoning and decision-making. The cutoff points for specific percentiles (questions f and g) indicate how these values distribute across a population. This informs expectations for individual pregnancy durations compared to societal averages.
Transcribed Image Text:### Understanding Pregnancy Duration and Probability The lengths of pregnancies are normally distributed with a mean of 280 days and a standard deviation of 16 days. The following problems help us explore probabilities related to the length of pregnancies. #### Questions: (a) **Probability of Shorter Pregnancy:** - Find the probability that an individual woman has a pregnancy shorter than 271 days. (b) **Probability for a Sample Mean:** - If 25 women are randomly selected, find the probability that they have a mean pregnancy shorter than 271 days. (c) **Methodological Differences:** - There should be a difference in your method for the previous two questions. Explain what you did differently for each problem and explain WHY your answers are different. (d) **Probability of Longer Pregnancy:** - Find the probability that an individual woman has a pregnancy longer than 300 days. (e) **Probability of Pregnancy Between Two Values:** - Find the probability that an individual woman has a pregnancy between 280 and 300 days. (f) **Cutoff for the Top 15%:** - What is the cutoff number of days for a pregnancy for the top 15% of women? (g) **Cutoff for the Bottom 20%:** - What is the cutoff number of days for a pregnancy for the bottom 20% of women? #### Explanation of Approaches: - **Calculating Probabilities for Individuals vs. Samples:** - For individual probabilities (questions a and d), use the standard normal distribution with the given mean and standard deviation. - For sample means (question b), use the standard error to adjust the standard deviation, as the sample size affects variability. - **Interpreting Results:** - Understanding how the probabilities reflect population characteristics helps in statistical reasoning and decision-making. The cutoff points for specific percentiles (questions f and g) indicate how these values distribute across a population. This informs expectations for individual pregnancy durations compared to societal averages.
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