1. **State the problem:** We want to find the probability that more than 2 parts are defective out of 7 parts produced by a machine that produces defective parts 12% of the time.
2. **Identify the distribution:** This is a binomial probability problem where the number of trials $n=7$, the probability of success (defective part) $p=0.12$, and we want $P(X>2)$ where $X$ is the number of defective parts.
3. **Formula:** The binomial probability formula is
$$P(X=k) = \binom{n}{k} p^k (1-p)^{n-k}$$
where $\binom{n}{k} = \frac{n!}{k!(n-k)!}$.
4. **Calculate $P(X>2)$:**
$$P(X>2) = 1 - P(X \leq 2) = 1 - [P(X=0) + P(X=1) + P(X=2)]$$
5. **Calculate each term:**
- $P(X=0) = \binom{7}{0} (0.12)^0 (0.88)^7 = 1 \times 1 \times 0.88^7 = 0.88^7$
- $P(X=1) = \binom{7}{1} (0.12)^1 (0.88)^6 = 7 \times 0.12 \times 0.88^6$
- $P(X=2) = \binom{7}{2} (0.12)^2 (0.88)^5 = 21 \times 0.12^2 \times 0.88^5$
6. **Calculate powers:**
- $0.88^7 = 0.4182$
- $0.88^6 = 0.4757$
- $0.88^5 = 0.5404$
7. **Calculate probabilities:**
- $P(X=0) = 0.4182$
- $P(X=1) = 7 \times 0.12 \times 0.4757 = 7 \times 0.0571 = 0.3997$
- $P(X=2) = 21 \times 0.0144 \times 0.5404 = 21 \times 0.00778 = 0.1634$
8. **Sum probabilities:**
$$P(X \leq 2) = 0.4182 + 0.3997 + 0.1634 = 0.9813$$
9. **Find final probability:**
$$P(X > 2) = 1 - 0.9813 = 0.0187$$
10. **Round to two decimal places:**
$$\boxed{0.02}$$
So, the probability that more than 2 parts are defective is approximately 0.02.
Defective Parts 68692A
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