Defective Tablets
1. The problem asks for the probability that in a sample of 25 tablets, two or more are defective, given a 5% defect rate per tablet.
2. Let $X$ be the number of defective tablets in the sample. $X$ follows a binomial distribution with parameters $n=25$ and $p=0.05$.
3. We want $P(X \geq 2)$. This is easier to find using the complement rule:
$$P(X \geq 2) = 1 - P(X < 2) = 1 - P(X=0) - P(X=1)$$
4. Calculate $P(X=0)$:
$$P(X=0) = \binom{25}{0} (0.05)^0 (0.95)^{25} = 1 \times 1 \times 0.95^{25} = 0.95^{25}$$
5. Calculate $P(X=1)$:
$$P(X=1) = \binom{25}{1} (0.05)^1 (0.95)^{24} = 25 \times 0.05 \times 0.95^{24}$$
6. Compute the values:
$$0.95^{25} \approx 0.2776$$
$$0.95^{24} \approx 0.2922$$
$$P(X=1) = 25 \times 0.05 \times 0.2922 = 1.25 \times 0.2922 = 0.3653$$
7. Now find $P(X \geq 2)$:
$$P(X \geq 2) = 1 - 0.2776 - 0.3653 = 1 - 0.6429 = 0.3571$$
8. Therefore, the probability that two or more tablets are defective in the sample is approximately $0.3571$.
Final answer: **0.3571**