Tensile Strength Scrap
1. **State the problem:** We have a metal component's tensile strength $X$ that is normally distributed with mean $\mu = 10000$ and standard deviation $\sigma = 100$. We want to find the proportion of components with tensile strength outside the range 9800 to 10200 inclusive, i.e., the scrap proportion.
2. **Convert the limits to standard normal variable $Z$:**
$$Z = \frac{X - \mu}{\sigma}$$
Calculate $Z$ for the lower limit 9800:
$$Z_{low} = \frac{9800 - 10000}{100} = \frac{-200}{100} = -2$$
Calculate $Z$ for the upper limit 10200:
$$Z_{high} = \frac{10200 - 10000}{100} = \frac{200}{100} = 2$$
3. **Find the probability that $Z$ lies between $-2$ and $2$:**
Using standard normal distribution tables or a calculator,
$$P(-2 \leq Z \leq 2) = P(Z \leq 2) - P(Z \leq -2)$$
From tables, $P(Z \leq 2) \approx 0.9772$ and $P(Z \leq -2) \approx 0.0228$
So,
$$P(-2 \leq Z \leq 2) = 0.9772 - 0.0228 = 0.9544$$
4. **Calculate the scrap proportion:**
The scrap proportion is the probability that $X$ is outside the range 9800 to 10200, which is
$$1 - 0.9544 = 0.0456$$
5. **Adjust for rounding to nearest 50:**
Since measurements are recorded to the nearest 50, the effective limits are 9800 and 10200 inclusive, so the scrap proportion remains approximately $0.0456$.
6. **Compare with given options:**
Closest option to $0.0456$ is d. 0.0542.
**Final answer:** d. 0.0542