Bus Lateness Probability
1. **State the problem:**
We want to find the probability that Joss is not late to work given the probabilities related to rain and bus lateness.
2. **Given data:**
- Probability it rains: $P(R) = 0.25$
- Probability bus is late if it rains: $P(L|R) = 0.4$
- Probability bus is late if it does not rain: $P(L|R^c) = 0.005$
3. **Find:**
The probability that Joss is not late, i.e., $P(L^c)$.
4. **Use the law of total probability:**
$$P(L) = P(L|R)P(R) + P(L|R^c)P(R^c)$$
where $P(R^c) = 1 - P(R) = 1 - 0.25 = 0.75$.
5. **Calculate $P(L)$:**
$$P(L) = (0.4)(0.25) + (0.005)(0.75) = 0.1 + 0.00375 = 0.10375$$
6. **Calculate $P(L^c)$:**
Since $P(L^c) = 1 - P(L)$,
$$P(L^c) = 1 - 0.10375 = 0.89625$$
7. **Interpretation:**
The probability that Joss is not late is approximately $0.896$ or 89.6%.