No Claim Probability
1. **Problem statement:** We want to find the probability that an insured who did not claim last year will not claim in the next 5 years.
2. **Define states:** Let:
- $N$: no accident occurred in the last year.
- $A$: accident occurred in the last year.
3. **Transition probabilities given:**
- $P(N \to A) = 0.04$ (4% chance of accident this year if no accident last year)
- $P(N \to N) = 1 - 0.04 = 0.96$
- $P(A \to A) = 0.12$ (12% chance of accident this year if accident last year)
- $P(A \to N) = 1 - 0.12 = 0.88$
4. **Initial state:** The insured did not claim last year, so we start in state $N$.
5. **Goal:** Find $P( ext{no claim in next 5 years} \mid ext{start in } N)$. "No claim" means staying in state $N$ every year for 5 years.
6. **Calculate step by step:** We want the probability that each year has no accident given the state transitions:
- Start at $N$ with probability 1.
- Year 1 no claim: $P(N \to N) = 0.96$
- Year 2 no claim: depends on previous year's state:
- Last year was $N$, next year no claim: $0.96$
- Last year was $A$, next year no claim: $0.88$
But to have no claim in both years, we must consider the joint probabilities of paths with no accidents.
7. **Derive probability of no claims recursively over 5 years:**
Let:
- $p_n(N)$ = Probability of no claim in year $n$ and being in state $N$ at year $n$.
- $p_n(A)$ = Probability of no claim in year $n$ and being in state $A$ at year $n$.
However, since no claim means staying in $N$, $p_n(A) = 0$ for all $n$.
So from state $N$:
- $p_1 = P(N \to N) = 0.96$
- $p_2 = p_1 \times 0.96 = 0.96^2$
- $p_3 = 0.96^3$
- $p_4 = 0.96^4$
- $p_5 = 0.96^5$
The result is because any accident ($A$) means a claim, so to have no claims, the insured must remain in $N$ all years.
8. **Final answer:**
$$
P(\text{no claim in 5 years} | N) = 0.96^5 = (0.96)^5
$$
Calculating numerically:
$$
0.96^5 = 0.8153726976 \approx 0.8154
$$
So the probability is approximately 0.8154 or 81.54%.