The blood platelet counts of a group of women have a bell-shaped distribution with a mean of 264.7 and a standard deviation of 64.4. (All units are 1000 cells/μL.) Using the empirical rule, find each approximate percentage below. a. What is the approximate percentage of women with platelet counts within 2 standard deviations of the mean, or between 135.9 and 393.5? b. What is the approximate percentage of women with platelet counts between 200.3 and 329.1? a. Approximately % of women in this group have platelet counts within 2 standard deviations of the mean, or between 135.9 and 393.5. (Type an integer or a decimal. Do not round.)

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## Empirical Rule and Blood Platelet Counts

### Context

The blood platelet counts of a group of women have a bell-shaped distribution with a mean of 264.7 and a standard deviation of 64.4. (All units are 1000 cells/μL.)

### Questions

**a. What is the approximate percentage of women with platelet counts within 2 standard deviations of the mean (between 135.9 and 393.5)?**

**b. What is the approximate percentage of women with platelet counts between 200.3 and 329.1?**

### Detailed Solution

**a.** The empirical rule (also known as the 68-95-99.7 rule) states that for a normal distribution:
- Approximately 68% of the data falls within 1 standard deviation of the mean.
- Approximately 95% of the data falls within 2 standard deviations of the mean.
- Approximately 99.7% of the data falls within 3 standard deviations of the mean.

Given that the mean is 264.7 and the standard deviation is 64.4, we calculate:

- \[ Mean - 2 \times \text{Standard Deviation} = 264.7 - 2 \times 64.4 = 135.9 \]
- \[ Mean + 2 \times \text{Standard Deviation} = 264.7 + 2 \times 64.4 = 393.5 \]

Hence, approximately **95%** of women in this group have platelet counts within this range.

---

In summary, the empirical rule helps to understand the distribution of data in a bell-shaped (normal) curve. In this case, approximately 95% of the women have blood platelet counts between 135.9 and 393.5 (thousand cells/μL).
Transcribed Image Text:## Empirical Rule and Blood Platelet Counts ### Context The blood platelet counts of a group of women have a bell-shaped distribution with a mean of 264.7 and a standard deviation of 64.4. (All units are 1000 cells/μL.) ### Questions **a. What is the approximate percentage of women with platelet counts within 2 standard deviations of the mean (between 135.9 and 393.5)?** **b. What is the approximate percentage of women with platelet counts between 200.3 and 329.1?** ### Detailed Solution **a.** The empirical rule (also known as the 68-95-99.7 rule) states that for a normal distribution: - Approximately 68% of the data falls within 1 standard deviation of the mean. - Approximately 95% of the data falls within 2 standard deviations of the mean. - Approximately 99.7% of the data falls within 3 standard deviations of the mean. Given that the mean is 264.7 and the standard deviation is 64.4, we calculate: - \[ Mean - 2 \times \text{Standard Deviation} = 264.7 - 2 \times 64.4 = 135.9 \] - \[ Mean + 2 \times \text{Standard Deviation} = 264.7 + 2 \times 64.4 = 393.5 \] Hence, approximately **95%** of women in this group have platelet counts within this range. --- In summary, the empirical rule helps to understand the distribution of data in a bell-shaped (normal) curve. In this case, approximately 95% of the women have blood platelet counts between 135.9 and 393.5 (thousand cells/μL).
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