1. **Problem statement:** Find the probability that the mean weight of 12 randomly selected men is greater than 167 pounds, given the population mean $\mu = 172$ and population standard deviation $\sigma = 29$. The sample size is $n = 12$.
2. **Formula and explanation:** For the sampling distribution of the sample mean, the standard deviation (standard error) is $\sigma_{\bar{x}} = \frac{\sigma}{\sqrt{n}}$.
The z-score formula for the sample mean is:
$$
Z = \frac{\bar{x} - \mu}{\sigma_{\bar{x}}} = \frac{\bar{x} - \mu}{\frac{\sigma}{\sqrt{n}}}
$$
3. **Calculate the standard error:**
$$
\sigma_{\bar{x}} = \frac{29}{\sqrt{12}} \approx \frac{29}{3.464} \approx 8.37
$$
4. **Calculate the z-score for $\bar{x} = 167$:**
$$
Z = \frac{167 - 172}{8.37} = \frac{-5}{8.37} \approx -0.60
$$
5. **Find the probability:**
The probability that the sample mean is greater than 167 is:
$$
P(\bar{x} > 167) = P(Z > -0.60)
$$
From standard normal tables or a calculator, $P(Z < -0.60) \approx 0.2743$, so
$$
P(Z > -0.60) = 1 - 0.2743 = 0.7257
$$
6. **Interpretation:**
There is approximately a 72.57% chance that the mean weight of 12 randomly selected men is greater than 167 pounds.
7. **Statement:**
If we randomly select 12 men, the probability that their average weight exceeds 167 pounds is about 72.57%. This means it is quite likely for the sample mean to be above 167.
Mean Weight Probability 9E615C
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