Fly Ball Probability
1. **Problem Statement:**
We have 49 fly balls with an average distance traveled, and we want to find the probability that the average distance is less than 222 feet.
2. **Given Information and Formula:**
Assuming the distances are normally distributed with mean $\mu$ and standard deviation $\sigma$, the sampling distribution of the sample mean $\bar{X}$ for $n=49$ balls has:
- Mean: $\mu_{\bar{X}} = \mu$
- Standard deviation (standard error): $\sigma_{\bar{X}} = \frac{\sigma}{\sqrt{n}}$
The probability we want is:
$$P(\bar{X} < 222) = P\left(Z < \frac{222 - \mu}{\sigma/\sqrt{49}}\right)$$
where $Z$ is a standard normal variable.
3. **Assuming values:**
Since the problem does not specify $\mu$ and $\sigma$, we infer from the graph scale (210 to 250) and typical baseball fly ball distances that:
- $\mu = 230$ feet
- $\sigma = 15$ feet
4. **Calculate the standard error:**
$$\sigma_{\bar{X}} = \frac{15}{\sqrt{49}} = \frac{15}{7} = 2.1429$$
5. **Calculate the Z-score:**
$$Z = \frac{222 - 230}{2.1429} = \frac{-8}{2.1429} \approx -3.73$$
6. **Find the probability:**
Using standard normal tables or a calculator:
$$P(Z < -3.73) \approx 0.0001$$
7. **Interpretation:**
The probability that the average distance of 49 balls is less than 222 feet is approximately 0.0001.
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**Part (c): Find the 70th percentile of the distribution of the average of 49 fly balls.**
1. The 70th percentile $P_{70}$ satisfies:
$$P(\bar{X} < P_{70}) = 0.70$$
2. Find the Z-score for 0.70:
$$Z_{0.70} \approx 0.524$$
3. Convert Z-score to $P_{70}$:
$$P_{70} = \mu + Z_{0.70} \times \sigma_{\bar{X}} = 230 + 0.524 \times 2.1429 \approx 230 + 1.12 = 231.12$$
**Final answers:**
- Probability that average is less than 222 feet: **0.0001**
- 70th percentile of average distance: **231.12 feet**
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**Graph description:**
The graph is a normal distribution curve with horizontal axis from 210 to 250.
- The region to the left of 222 is shaded (top-left graph) representing the probability in part (b).