1. **State the problem:** We need to determine for which binomial distributions the normal distribution is not a reasonable approximation.
2. **Recall the rule:** The normal approximation to the binomial distribution is reasonable if both $np \geq 10$ and $n(1-p) \geq 10$.
3. **Calculate for each distribution:**
- For $n=75$, $p=0.11$:
$$np = 75 \times 0.11 = 8.25$$
$$n(1-p) = 75 \times 0.89 = 66.75$$
Since $np = 8.25 < 10$, normal approximation is **not** reasonable.
- For $n=50$, $p=0.4$:
$$np = 50 \times 0.4 = 20$$
$$n(1-p) = 50 \times 0.6 = 30$$
Both are $\geq 10$, so normal approximation is reasonable.
- For $n=40$, $p=0.8$:
$$np = 40 \times 0.8 = 32$$
$$n(1-p) = 40 \times 0.2 = 8$$
Since $n(1-p) = 8 < 10$, normal approximation is **not** reasonable.
- For $n=40$, $p=0.12$:
$$np = 40 \times 0.12 = 4.8$$
$$n(1-p) = 40 \times 0.88 = 35.2$$
Since $np = 4.8 < 10$, normal approximation is **not** reasonable.
4. **Conclusion:** The normal distribution is not a reasonable approximation for:
- $n=75$, $p=0.11$
- $n=40$, $p=0.8$
- $n=40$, $p=0.12$
Only for $n=50$, $p=0.4$ is the normal approximation reasonable.
Normal Approximation 5C24Cd
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