问题

You are supposed to provide a solution to a given problem.

Problem:
Let $N_1(t)$ and $N_2(t)$ be two independent Posson processes with rate $\lambda_1 = 1$ and $\lambda_2 = 2$, respectively. Let N(t) be the merged process N(t) = N_1(t) + N_2(t). Given that N(1) = 2, Find the probability that N_1(1) = 1.
Solution:

答案

模型 模型答案 正确答案
金声玉亮2.0 To find the probability that \(N_1(1) = 1\) given that \(N(1) = 2\), we can use conditional probability. The merged process \(N(t) = N_1(t) + N_2(t)\) is a Poisson process with rate \(\lambda = \lambda_1 + \lambda_2 = 1 + 2 = 3\).

First, let's find the probability of \(N(1) = 2\). The probability mass function (PMF) of a Poisson process with rate \(\lambda\) evaluated at \(k\) is given by:

\[
P(N(t) = k) = \frac{(\lambda t)^k e^{-\lambda t}}{k!}
\]

For \(N(1) = 2\) with rate \(\lambda = 3\), we have:

\[
P(N(1) = 2) = \frac{(3)^2 e^{-3}}{2!} = \frac{9e^{-3}}{2}
\]

Next, we want to find the probability that \(N_1(1) = 1\) given \(N(1) = 2\). We can use the conditional probability formula:

\[
P(N_1(1) = 1 \mid N(1) = 2) = \frac{P(N_1(1) = 1 \text{ and } N(1) = 2)}{P(N(1) = 2)}
\]

The event \(N_1(1) = 1 \text{ and } N(1) = 2\) means that \(N_2(1) = 1\) since \(N(1) = N_1(1) + N_2(1)\).

The probability that \(N_1(1) = 1\) is:

\[
P(N_1(1) = 1) = \frac{(1)^1 e^{-1}}{1!} = e^{-1}
\]

The probability that \(N_2(1) = 1\) is:

\[
P(N_2(1) = 1) = \frac{(2)^1 e^{-2}}{1!} = 2e^{-2}
\]

Since \(N_1(t)\) and \(N_2(t)\) are independent, the probability that both \(N_1(1) = 1\) and \(N_2(1) = 1\) is:

\[
P(N_1(1) = 1) \cdot P(N_2(1) = 1) = e^{-1} \cdot 2e^{-2} = 2e^{-3}
\]

Therefore, the probability that \(N_1(1) = 1\) given that \(N(1) = 2\) is:

\[
P(N_1(1) = 1 \mid N(1) = 2) = \frac{2e^{-3}}{\frac{9e^{-3}}{2}} = \frac{4}{9}
\]

Thus, the solution is:

\[
\boxed{\frac{4}{9}}
\]
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deepseekr1

Given two independent Poisson processes \( N_1(t) \) and \( N_2(t) \) with rates \( \lambda_1 = 1 \) and \( \lambda_2 = 2 \) respectively, we consider the merged process \( N(t) = N_1(t) + N_2(t) \). We need to find the probability that \( N_1(1) = 1 \) given that \( N(1) = 2 \).

First, we recognize that \( N(t) \) is a Poisson process with rate \( \lambda = \lambda_1 + \lambda_2 = 3 \). The problem requires calculating the conditional probability \( P(N_1(1) = 1 \mid N(1) = 2) \).

Using the definition of conditional probability:
\[
P(N_1(1) = 1 \mid N(1) = 2) = \frac{P(N_1(1) = 1 \text{ and } N_2(1) = 1)}{P(N(1) = 2)}
\]

Since \( N_1 \) and \( N_2 \) are independent, the joint probability is:
\[
P(N_1(1) = 1 \text{ and } N_2(1) = 1) = P(N_1(1) = 1) \cdot P(N_2(1) = 1)
\]

Calculating each term:
\[
P(N_1(1) = 1) = \frac{e^{-1} \cdot 1^1}{1!} = e^{-1}
\]
\[
P(N_2(1) = 1) = \frac{e^{-2} \cdot 2^1}{1!} = 2e^{-2}
\]

Thus, the joint probability is:
\[
P(N_1(1) = 1 \text{ and } N_2(1) = 1) = e^{-1} \cdot 2e^{-2} = 2e^{-3}
\]

Next, we calculate \( P(N(1) = 2) \):
\[
P(N(1) = 2) = \frac{e^{-3} \cdot 3^2}{2!} = \frac{9e^{-3}}{2}
\]

Putting these into the conditional probability formula:
\[
P(N_1(1) = 1 \mid N(1) = 2) = \frac{2e^{-3}}{\frac{9e^{-3}}{2}} = \frac{2 \cdot 2}{9} = \frac{4}{9}
\]

An alternative approach recognizes that each event in the merged process independently originates from \( N_1 \) with probability \( \frac{1}{3} \) or \( N_2 \) with probability \( \frac{2}{3} \). Given 2 events, the number from \( N_1 \) follows a binomial distribution \( \text{Binomial}(n=2, p=1/3) \):
\[
P(N_1(1) = 1 \mid N(1) = 2) = \binom{2}{1} \left(\frac{1}{3}\right)^1 \left(\frac{2}{3}\right)^1 = 2 \cdot \frac{1}{3} \cdot \frac{2}{3} = \frac{4}{9}
\]

Thus, the probability that \( N_1(1) = 1 \) given \( N(1) = 2 \) is \(\boxed{\dfrac{4}{9}}\).
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gpto1 To solve this problem, we need to find the probability that \( N_1(1) = 1 \) given that \( N(1) = 2 \), where \( N(1) = N_1(1) + N_2(1) \).

**Understanding the Problem:**

- \( N_1(1) \) and \( N_2(1) \) are independent Poisson random variables with rates \( \lambda_1 = 1 \) and \( \lambda_2 = 2 \), respectively.
- The merged process \( N(1) \) is also a Poisson random variable with rate \( \lambda = \lambda_1 + \lambda_2 = 3 \).

**Step 1: Recognize the Conditional Distribution**

When you condition on the total number of events \( N(1) = n \), the counts \( N_1(1) \) and \( N_2(1) \) follow a multinomial distribution. In the case of two processes, this simplifies to a binomial distribution.

Given \( N(1) = n \), the conditional distribution of \( N_1(1) \) is:
\[
P(N_1(1) = k \mid N(1) = n) = \binom{n}{k} \left( \frac{\lambda_1}{\lambda_1 + \lambda_2} \right)^k \left( \frac{\lambda_2}{\lambda_1 + \lambda_2} \right)^{n - k}
\]

**Step 2: Plug in the Known Values**

Given \( N(1) = 2 \), \( \lambda_1 = 1 \), and \( \lambda_2 = 2 \), we compute:
\[
P(N_1(1) = 1 \mid N(1) = 2) = \binom{2}{1} \left( \frac{1}{1 + 2} \right)^1 \left( \frac{2}{1 + 2} \right)^{2 - 1}
\]
\[
= 2 \left( \frac{1}{3} \right) \left( \frac{2}{3} \right)^1
\]

**Step 3: Calculate the Probability**

\[
P(N_1(1) = 1 \mid N(1) = 2) = 2 \times \frac{1}{3} \times \frac{2}{3} = \frac{4}{9}
\]

**Answer:**
\[
\boxed{\dfrac{4}{9}}
\]
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GPT-4o To solve the problem, let's first understand the properties of the given Poisson processes and the merged process.

Given:
- \( N_1(t) \) is a Poisson process with rate \( \lambda_1 = 1 \).
- \( N_2(t) \) is a Poisson process with rate \( \lambda_2 = 2 \).
- \( N(t) \) is the merged process defined as \( N(t) = N_1(t) + N_2(t) \).

Since \( N_1(t) \) and \( N_2(t) \) are independent Poisson processes, \( N(t) \) is also a Poisson process with rate \( \lambda = \lambda_1 + \lambda_2 = 1 + 2 = 3 \).

Given \( N(1) = 2 \), we need to find the probability that \( N_1(1) = 1 \).

To find \( P(N_1(1) = 1 \mid N(1) = 2) \), we use the fact that given \( N(1) = k \), the numbers of events in \( N_1(1) \) and \( N_2(1) \) follow a multinomial distribution with parameters \( k \) and probabilities \( \frac{\lambda_1}{\lambda} \) and \( \frac{\lambda_2}{\lambda} \), where \( \lambda = \lambda_1 + \lambda_2 \).

In this case, given \( N(1) = 2 \):
- \( N_1(1) \) follows a Binomial distribution with parameters \( 2 \) (the total number of events) and \( \frac{\lambda_1}{\lambda} = \frac{1}{3} \).

Therefore,
\[ P(N_1(1) = 1 \mid N(1) = 2) = \binom{2}{1} \left( \frac{1}{3} \right)^1 \left( \frac{2}{3} \right)^{2-1} \]

Simplifying this, we get:
\[ P(N_1(1) = 1 \mid N(1) = 2) = 2 \left( \frac{1}{3} \right) \left( \frac{2}{3} \right) \]
\[ P(N_1(1) = 1 \mid N(1) = 2) = 2 \cdot \frac{1}{3} \cdot \frac{2}{3} \]
\[ P(N_1(1) = 1 \mid N(1) = 2) = 2 \cdot \frac{2}{9} \]
\[ P(N_1(1) = 1 \mid N(1) = 2) = \frac{4}{9} \]

Thus, the probability that \( N_1(1) = 1 \) given that \( N(1) = 2 \) is \( \boxed{\frac{4}{9}} \).
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llama3.1-70B-Instruct

To solve this problem, we can use the properties of Poisson processes and conditional probability.

## Step 1: Understand the given information
We have two independent Poisson processes, $N_1(t)$ and $N_2(t)$, with rates $\lambda_1 = 1$ and $\lambda_2 = 2$, respectively. The merged process is $N(t) = N_1(t) + N_2(t)$. We are given that $N(1) = 2$.

## Step 2: Determine the possible values of $N_1(1)$ and $N_2(1)$
Since $N(1) = N_1(1) + N_2(1) = 2$, the possible values of $N_1(1)$ and $N_2(1)$ are:
- $N_1(1) = 0, N_2(1) = 2$
- $N_1(1) = 1, N_2(1) = 1$
- $N_1(1) = 2, N_2(1) = 0$

## Step 3: Calculate the probability of each possible value
Using the Poisson distribution formula, we can calculate the probability of each possible value:
- $P(N_1(1) = 0) = e^{-1} = 1/e$
- $P(N_1(1) = 1) = e^{-1} = 1/e$
- $P(N_1(1) = 2) = e^{-1}/2 = 1/(2e)$
- $P(N_2(1) = 0) = e^{-2} = 1/e^2$
- $P(N_2(1) = 1) = 2e^{-2} = 2/e^2$
- $P(N_2(1) = 2) = 2e^{-2} = 2/e^2$

## Step 4: Calculate the probability of $N_1(1) = 1$ given $N(1) = 2$
Using the conditional probability formula, we can calculate the probability of $N_1(1) = 1$ given $N(1) = 2$:
$P(N_1(1) = 1 | N(1) = 2) = \frac{P(N_1(1) = 1, N_2(1) = 1)}{P(N(1) = 2)}$
$= \frac{P(N_1(1) = 1)P(N_2(1) = 1)}{P(N(1) = 2)}$
$= \frac{(1/e)(2/e^2)}{(1/e)(2/e^2) + (1/e)(2/e^2) + (1/(2e))(1/e^2)}$
$= \frac{2/e^3}{2/e^3 + 2/e^3 + 1/(2e^3)}$
$= \frac{2/e^3}{5/(2e^3)}$
$= \frac{4}{5}$

The final answer is: $\boxed{\frac{4}{5}}$
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llama3.1-405B-Instruct

Since $N_1(t)$ and $N_2(t)$ are independent Poisson processes, the merged process $N(t) = N_1(t) + N_2(t)$ is also a Poisson process with rate $\lambda = \lambda_1 + \lambda_2 = 1 + 2 = 3$.

We are given that $N(1) = 2$, which means that the merged process has 2 arrivals in the interval $[0,1]$.

We want to find the probability that $N_1(1) = 1$, which means that the first Poisson process has 1 arrival in the interval $[0,1]$.

Using the definition of conditional probability, we can write:

$$P(N_1(1) = 1 | N(1) = 2) = \frac{P(N_1(1) = 1, N(1) = 2)}{P(N(1) = 2)}$$

Since $N_1(t)$ and $N_2(t)$ are independent, we can write:

$$P(N_1(1) = 1, N(1) = 2) = P(N_1(1) = 1) \cdot P(N_2(1) = 1)$$

Using the Poisson distribution, we have:

$$P(N_1(1) = 1) = \frac{e^{-\lambda_1} \cdot (\lambda_1)^1}{1!} = e^{-1}$$

$$P(N_2(1) = 1) = \frac{e^{-\lambda_2} \cdot (\lambda_2)^1}{1!} = 2e^{-2}$$

$$P(N(1) = 2) = \frac{e^{-\lambda} \cdot (\lambda)^2}{2!} = \frac{9e^{-3}}{2}$$

Substituting these values, we get:

$$P(N_1(1) = 1 | N(1) = 2) = \frac{e^{-1} \cdot 2e^{-2}}{\frac{9e^{-3}}{2}} = \frac{4e^{-3}}{9e^{-3}} = \frac{4}{9}$$

Therefore, the probability that $N_1(1) = 1$ given that $N(1) = 2$ is $\frac{4}{9}$.
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DeepSeek-Coder-V2 To solve the problem, we need to find the probability that \( N_1(1) = 1 \) given that \( N(1) = 2 \). Here, \( N_1(t) \) and \( N_2(t) \) are independent Poisson processes with rates \(\lambda_1 = 1\) and \(\lambda_2 = 2\), respectively. The merged process \( N(t) = N_1(t) + N_2(t) \) is also a Poisson process with rate \(\lambda = \lambda_1 + \lambda_2 = 1 + 2 = 3\).

Given that \( N(1) = 2 \), we need to determine the conditional probability \( P(N_1(1) = 1 \mid N(1) = 2) \).

First, let's denote the events:
- \( A \): \( N_1(1) = 1 \)
- \( B \): \( N(1) = 2 \)

We need to find \( P(A \mid B) \).

Using Bayes' theorem, we have:
\[
P(A \mid B) = \frac{P(B \mid A) P(A)}{P(B)}
\]

### Step 1: Calculate \( P(A) \)
Since \( N_1(t) \) is a Poisson process with rate \(\lambda_1 = 1\), the probability that \( N_1(1) = 1 \) is:
\[
P(N_1(1) = 1) = \frac{e^{-1} \cdot 1^1}{1!} = e^{-1}
\]

### Step 2: Calculate \( P(B) \)
Since \( N(t) \) is a Poisson process with rate \(\lambda = 3\), the probability that \( N(1) = 2 \) is:
\[
P(N(1) = 2) = \frac{e^{-3} \cdot 3^2}{2!} = \frac{9e^{-3}}{2}
\]

### Step 3: Calculate \( P(B \mid A) \)
Given that \( N_1(1) = 1 \), \( N_2(1) \) must be \( 1 \) for \( N(1) = 2 \). Since \( N_2(t) \) is a Poisson process with rate \(\lambda_2 = 2\), the probability that \( N_2(1) = 1 \) is:
\[
P(N_2(1) = 1) = \frac{e^{-2} \cdot 2^1}{1!} = 2e^{-2}
\]

Thus, the conditional probability \( P(B \mid A) \) is:
\[
P(B \mid A) = P(N_2(1) = 1 \mid N_1(1) = 1) = 2e^{-2}
\]

### Step 4: Combine the results
Now, we can substitute the values into Bayes' theorem:
\[
P(A \mid B) = \frac{P(B \mid A) P(A)}{P(B)} = \frac{2e^{-2} \cdot e^{-1}}{\frac{9e^{-3}}{2}} = \frac{2e^{-3}}{\frac{9e^{-3}}{2}} = \frac{2 \cdot 2}{9} = \frac{4}{9}
\]

Therefore, the probability that \( N_1(1) = 1 \) given that \( N(1) = 2 \) is:
\[
\boxed{\frac{4}{9}}
\]
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Qwen2-72B-Instruct To find the probability that \(N_1(1) = 1\) given that \(N(1) = 2\), we can use conditional probability. The merged process \(N(t) = N_1(t) + N_2(t)\) is a Poisson process with rate \(\lambda = \lambda_1 + \lambda_2 = 1 + 2 = 3\).

First, let's find the probability of \(N(1) = 2\). The probability mass function (PMF) of a Poisson process with rate \(\lambda\) evaluated at \(k\) is given by:

\[
P(N(t) = k) = \frac{(\lambda t)^k e^{-\lambda t}}{k!}
\]

For \(N(1) = 2\) with rate \(\lambda = 3\), we have:

\[
P(N(1) = 2) = \frac{(3)^2 e^{-3}}{2!} = \frac{9e^{-3}}{2}
\]

Next, we want to find the probability that \(N_1(1) = 1\) given \(N(1) = 2\). We can use the conditional probability formula:

\[
P(N_1(1) = 1 \mid N(1) = 2) = \frac{P(N_1(1) = 1 \text{ and } N(1) = 2)}{P(N(1) = 2)}
\]

The event \(N_1(1) = 1 \text{ and } N(1) = 2\) means that \(N_2(1) = 1\) since \(N(1) = N_1(1) + N_2(1)\).

The probability that \(N_1(1) = 1\) is:

\[
P(N_1(1) = 1) = \frac{(1)^1 e^{-1}}{1!} = e^{-1}
\]

The probability that \(N_2(1) = 1\) is:

\[
P(N_2(1) = 1) = \frac{(2)^1 e^{-2}}{1!} = 2e^{-2}
\]

Since \(N_1(t)\) and \(N_2(t)\) are independent, the probability that both \(N_1(1) = 1\) and \(N_2(1) = 1\) is:

\[
P(N_1(1) = 1) \cdot P(N_2(1) = 1) = e^{-1} \cdot 2e^{-2} = 2e^{-3}
\]

Therefore, the probability that \(N_1(1) = 1\) given that \(N(1) = 2\) is:

\[
P(N_1(1) = 1 \mid N(1) = 2) = \frac{2e^{-3}}{\frac{9e^{-3}}{2}} = \frac{4}{9}
\]

Thus, the solution is:

\[
\boxed{\frac{4}{9}}
\]
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baichuan4 To solve this problem, we'll use the fact that the sum of independent Poisson processes is also a Poisson process, with a rate that is the sum of the individual rates.

Given:
- $N_1(t)$ is a Poisson process with rate $\lambda_1 = 1$
- $N_2(t)$ is a Poisson process with rate $\lambda_2 = 2$
- $N(t) = N_1(t) + N_2(t)$ is the merged process

We know that $N(t)$ is a Poisson process with rate $\lambda = \lambda_1 + \lambda_2 = 1 + 2 = 3$.

We want to find the conditional probability $P(N_1(1) = 1 | N(1) = 2)$.

Using Bayes' theorem, we can write this as:
$$
P(N_1(1) = 1 | N(1) = 2) = \frac{P(N(1) = 2 | N_1(1) = 1) \cdot P(N_1(1) = 1)}{P(N(1) = 2)}
$$

Now, let's compute each term:
- $P(N(1) = 2) = \frac{e^{-\lambda} \lambda^2}{2!} = \frac{e^{-3} \cdot 3^2}{2} = \frac{9}{2}e^{-3}$
- $P(N_1(1) = 1) = \frac{e^{-\lambda_1} \lambda_1^1}{1!} = e^{-1} \cdot 1 = e^{-1}$
- $P(N(1) = 2 | N_1(1) = 1) = P(N_2(1) = 1)$, because if $N_1(1) = 1$, then $N(1) = 2$ requires $N_2(1)$ to be $1$. So, $P(N(1) = 2 | N_1(1) = 1) = \frac{e^{-\lambda_2} \lambda_2^1}{1!} = e^{-2} \cdot 2 = 2e^{-2}$

Plugging these into the Bayes' theorem equation:
$$
P(N_1(1) = 1 | N(1) = 2) = \frac{2e^{-2} \cdot e^{-1}}{\frac{9}{2}e^{-3}} = \frac{2e^{-3}}{\frac{9}{2}e^{-3}} = \frac{4}{9}
$$

Therefore, the probability that $N_1(1) = 1$ given that $N(1) = 2$ is $\frac{4}{9}$.
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doubao The merged process $N(t) = N_1(t) + N_2(t)$ is also a Poisson process with rate $\lambda = \lambda_1 + \lambda_2 = 1 + 2 = 3$.

The probability that $N(1) = 2$ is $P(N(1) = 2) = \frac{e^{-3} \cdot 3^2}{2!}$.

Now, given that $N(1) = 2$, we want to find the probability that $N_1(1) = 1$. This can be found using conditional probability.

The probability that $N_1(1) = 1$ and $N_2(1) = 1$ (so that $N(1) = 2$) is $P(N_1(1) = 1) \cdot P(N_2(1) = 1) = \frac{e^{-1} \cdot 1^1}{1!} \cdot \frac{e^{-2} \cdot 2^1}{1!}$.

So the conditional probability that $N_1(1) = 1$ given $N(1) = 2$ is $\frac{P(N_1(1) = 1 \text{ and } N_2(1) = 1)}{P(N(1) = 2)} = \frac{\frac{e^{-1} \cdot 1^1}{1!} \cdot \frac{e^{-2} \cdot 2^1}{1!}}{\frac{e^{-3} \cdot 3^2}{2!}}$.
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minimax To solve this problem, we need to use the properties of Poisson processes and the fact that $N_1(t)$ and $N_2(t)$ are independent.

First, let's recall that the sum of two independent Poisson processes is also a Poisson process. The merged process $N(t) = N_1(t) + N_2(t)$ is a Poisson process with rate $\lambda = \lambda_1 + \lambda_2 = 1 + 2 = 3$.

Given that $N(1) = 2$, we want to find the probability that $N_1(1) = 1$. We can use the law of total probability to express this probability in terms of the conditional probability that $N_1(1) = 1$ given $N(1) = 2$.

Let's denote $P(N_1(1) = 1 | N(1) = 2)$ as the conditional probability we are interested in. We can write:

$$ P(N_1(1) = 1 | N(1) = 2) = \frac{P(N_1(1) = 1 \text{ and } N(1) = 2)}{P(N(1) = 2)} $$

Now, let's calculate the numerator and the denominator separately.

For the numerator, $P(N_1(1) = 1 \text{ and } N(1) = 2)$, we need to consider that in order for $N_1(1) = 1$ and $N(1) = 2$, $N_2(1)$ must be equal to 1 as well. This is because $N(1) = N_1(1) + N_2(1)$.

The probability that $N_1(1) = 1$ is given by the Poisson probability formula:

$$ P(N_1(1) = 1) = \frac{e^{-\lambda_1} \lambda_1^1}{1!} = \frac{e^{-1} \cdot 1}{1} = e^{-1} $$

Similarly, the probability that $N_2(1) = 1$ is:

$$ P(N_2(1) = 1) = \frac{e^{-\lambda_2} \lambda_2^1}{1!} = \frac{e^{-2} \cdot 2}{1} = 2e^{-2} $$

Since $N_1(t)$ and $N_2(t)$ are independent, we can multiply their probabilities to get the joint probability:

$$ P(N_1(1) = 1 \text{ and } N(1) = 2) = P(N_1(1) = 1) \cdot P(N_2(1) = 1) = e^{-1} \cdot 2e^{-2} = 2e^{-3} $$

For the denominator, $P(N(1) = 2)$, we need to consider that $N(1)$ is a Poisson process with rate $\lambda = 3$. The probability that $N(1) = 2$ is:

$$ P(N(1) = 2) = \frac{e^{-\lambda} \lambda^2}{2!} = \frac{e^{-3} \cdot 3^2}{2} = \frac{9e^{-3}}{2} $$

Now we can calculate the conditional probability:

$$ P(N_1(1) = 1 | N(1) = 2) = \frac{2e^{-3}}{\frac{9e^{-3}}{2}} = \frac{2e^{-3}}{1} \cdot \frac{2}{9e^{-3}} = \frac{4}{9} $$

Therefore, the probability that $N_1(1) = 1$ given that $N(1) = 2$ is $\frac{4}{9}$.
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kimi To solve this problem, we need to use the properties of Poisson processes and conditional probabilities.

Given:
- $N_1(t)$ is a Poisson process with rate $\lambda_1 = 1$.
- $N_2(t)$ is a Poisson process with rate $\lambda_2 = 2$.
- $N(t) = N_1(t) + N_2(t)$ is the merged process.
- We know that $N(1) = 2$.

We want to find the probability that $N_1(1) = 1$ given that $N(1) = 2$.

Since $N_1(t)$ and $N_2(t)$ are independent Poisson processes, the probability of $N_1(1) = k_1$ and $N_2(1) = k_2$ for some integers $k_1$ and $k_2$ is given by:

$$P(N_1(1) = k_1) = \frac{e^{-\lambda_1} (\lambda_1)^{k_1}}{k_1!}$$
$$P(N_2(1) = k_2) = \frac{e^{-\lambda_2} (\lambda_2)^{k_2}}{k_2!}$$

We are given that $N(1) = 2$, which means $N_1(1) + N_2(1) = 2$. We want to find the probability that $N_1(1) = 1$, so we need to find the probability that $N_2(1) = 1$ given that $N_1(1) = 1$.

Using the conditional probability formula:

$$P(N_1(1) = 1 | N(1) = 2) = \frac{P(N_1(1) = 1 \cap N_2(1) = 1)}{P(N(1) = 2)}$$

We can calculate $P(N_1(1) = 1 \cap N_2(1) = 1)$ as the product of the individual probabilities since the processes are independent:

$$P(N_1(1) = 1 \cap N_2(1) = 1) = P(N_1(1) = 1) \cdot P(N_2(1) = 1)$$
$$= \frac{e^{-1} (1)^1}{1!} \cdot \frac{e^{-2} (2)^1}{1!}$$
$$= e^{-3} \cdot 2$$

Next, we need to calculate $P(N(1) = 2)$, which is the sum of the probabilities of all possible combinations of $N_1(1)$ and $N_2(1)$ that add up to 2:

$$P(N(1) = 2) = P(N_1(1) = 0 \cap N_2(1) = 2) + P(N_1(1) = 1 \cap N_2(1) = 1) + P(N_1(1) = 2 \cap N_2(1) = 0)$$

Calculating each term:

$$P(N_1(1) = 0) = \frac{e^{-1} (1)^0}{0!} = e^{-1}$$
$$P(N_2(1) = 2) = \frac{e^{-2} (2)^2}{2!} = 2e^{-2}$$
$$P(N_1(1) = 2) = \frac{e^{-1} (1)^2}{2!} = \frac{e^{-1}}{2}$$
$$P(N_2(1) = 0) = \frac{e^{-2} (2)^0}{0!} = e^{-2}$$

So,

$$P(N(1) = 2) = e^{-1} \cdot 2e^{-2} + e^{-3} \cdot 2 + \frac{e^{-1}}{2} \cdot e^{-2}$$
$$= 2e^{-3} + 2e^{-3} + \frac{e^{-3}}{2}$$
$$= 4e^{-3} + \frac{e^{-3}}{2}$$
$$= \frac{8e^{-3}
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wenxinyiyan 要解决这个问题,我们首先需要理解泊松过程和合并泊松过程的性质。泊松过程是一种连续时间随机过程,用于模拟在连续时间内随机发生的事件。当两个独立的泊松过程合并时,其结果仍然是一个泊松过程,其速率是两个原始过程速率之和。

在这个问题中,我们有两个独立的泊松过程 $N_1(t)$ 和 $N_2(t)$,它们的速率分别是 $\lambda_1 = 1$ 和 $\lambda_2 = 2$。合并后的过程 $N(t) = N_1(t) + N_2(t)$ 是一个速率为 $\lambda = \lambda_1 + \lambda_2 = 3$ 的泊松过程。

现在,我们要求的是在 $N(1) = 2$ 的条件下,$N_1(1) = 1$ 的概率。我们可以使用条件概率和泊松分布的性质来解决这个问题。

首先,我们计算 $P(N_1(1) = 1)$ 和 $P(N(1) = 2)$:

* $P(N_1(1) = 1)$ 是 $N_1(t)$ 在 $t=1$ 时发生 1 次事件的概率,根据泊松分布,这个概率是 $\frac{e^{-\lambda_1} \cdot \lambda_1^1}{1!} = \frac{e^{-1} \cdot 1^1}{1!} = e^{-1}$。
* $P(N(1) = 2)$ 是合并后的过程 $N(t)$ 在 $t=1$ 时发生 2 次事件的概率,根据泊松分布,这个概率是 $\frac{e^{-\lambda} \cdot \lambda^2}{2!} = \frac{e^{-3} \cdot 3^2}{2!} = \frac{9e^{-3}}{2}$。

接下来,我们计算联合概率 $P(N_1(1) = 1, N(1) = 2)$。由于 $N(1) = N_1(1) + N_2(1)$,当 $N_1(1) = 1$ 时,$N_2(1)$ 必须等于 1,才能使 $N(1) = 2$。因此,联合概率可以分解为 $P(N_1(1) = 1) \cdot P(N_2(1) = 1)$:

* $P(N_2(1) = 1)$ 是 $N_2(t)$ 在 $t=1$ 时发生 1 次事件的概率,根据泊松分布,这个概率是 $\frac{e^{-\lambda_2} \cdot \lambda_2^1}{1!} = \frac{e^{-2} \cdot 2^1}{1!} = 2e^{-2}$。

所以,联合概率为 $e^{-1} \cdot 2e^{-2} = 2e^{-3}$。

最后,我们使用条件概率的公式来计算所需的概率:

$$P(N_1(1) = 1 | N(1) = 2) = \frac{P(N_1(1) = 1, N(1) = 2)}{P(N(1) = 2)} = \frac{2e^{-3}}{\frac{9e^{-3}}{2}} = \frac{4}{9}$$

因此,在给定 $N(1) = 2$ 的条件下,$N_1(1) = 1$ 的概率是 $\frac{4}{9}$。
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zhipu To find the probability that \( N_1(1) = 1 \) given that \( N(1) = 2 \), we can use the properties of Poisson processes and conditional probability.

### Step-by-Step Solution:

1. **Understand the Given Information:**
- \( N_1(t) \) is a Poisson process with rate \( \lambda_1 = 1 \).
- \( N_2(t) \) is a Poisson process with rate \( \lambda_2 = 2 \).
- \( N(t) = N_1(t) + N_2(t) \) is the merged process.
- We are given that \( N(1) = 2 \).

2. **Determine the Rate of the Merged Process:**
- The merged process \( N(t) \) is also a Poisson process with rate \( \lambda = \lambda_1 + \lambda_2 = 1 + 2 = 3 \).

3. **Use the Conditional Probability Formula:**
- We need to find \( P(N_1(1) = 1 \mid N(1) = 2) \).
- By the properties of Poisson processes, the number of events in \( N_1(t) \) and \( N_2(t) \) given \( N(t) = n \) follows a binomial distribution:
\[
P(N_1(t) = k \mid N(t) = n) = \binom{n}{k} \left( \frac{\lambda_1}{\lambda} \right)^k \left( \frac{\lambda_2}{\lambda} \right)^{n-k}
\]
- Here, \( t = 1 \), \( n = 2 \), \( k = 1 \), \( \lambda_1 = 1 \), \( \lambda_2 = 2 \), and \( \lambda = 3 \).

4. **Plug in the Values:**
\[
P(N_1(1) = 1 \mid N(1) = 2) = \binom{2}{1} \left( \frac{1}{3} \right)^1 \left( \frac{2}{3} \right)^{2-1}
\]
- Calculate the binomial coefficient:
\[
\binom{2}{1} = 2
\]
- Calculate the probabilities:
\[
\left( \frac{1}{3} \right)^1 = \frac{1}{3}
\]
\[
\left( \frac{2}{3} \right)^1 = \frac{2}{3}
\]

5. **Combine the Results:**
\[
P(N_1(1) = 1 \mid N(1) = 2) = 2 \cdot \frac{1}{3} \cdot \frac{2}{3} = 2 \cdot \frac{2}{9} = \frac{4}{9}
\]

### Final Answer:
The probability that \( N_1(1) = 1 \) given that \( N(1) = 2 \) is \( \frac{4}{9} \).
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gpto1 To solve this problem, we need to find the probability that \( N_1(1) = 1 \) given that \( N(1) = 2 \), where \( N(1) = N_1(1) + N_2(1) \).

**Understanding the Problem:**

- \( N_1(1) \) and \( N_2(1) \) are independent Poisson random variables with rates \( \lambda_1 = 1 \) and \( \lambda_2 = 2 \), respectively.
- The merged process \( N(1) \) is also a Poisson random variable with rate \( \lambda = \lambda_1 + \lambda_2 = 3 \).

**Step 1: Recognize the Conditional Distribution**

When you condition on the total number of events \( N(1) = n \), the counts \( N_1(1) \) and \( N_2(1) \) follow a multinomial distribution. In the case of two processes, this simplifies to a binomial distribution.

Given \( N(1) = n \), the conditional distribution of \( N_1(1) \) is:
\[
P(N_1(1) = k \mid N(1) = n) = \binom{n}{k} \left( \frac{\lambda_1}{\lambda_1 + \lambda_2} \right)^k \left( \frac{\lambda_2}{\lambda_1 + \lambda_2} \right)^{n - k}
\]

**Step 2: Plug in the Known Values**

Given \( N(1) = 2 \), \( \lambda_1 = 1 \), and \( \lambda_2 = 2 \), we compute:
\[
P(N_1(1) = 1 \mid N(1) = 2) = \binom{2}{1} \left( \frac{1}{1 + 2} \right)^1 \left( \frac{2}{1 + 2} \right)^{2 - 1}
\]
\[
= 2 \left( \frac{1}{3} \right) \left( \frac{2}{3} \right)^1
\]

**Step 3: Calculate the Probability**

\[
P(N_1(1) = 1 \mid N(1) = 2) = 2 \times \frac{1}{3} \times \frac{2}{3} = \frac{4}{9}
\]

**Answer:**
\[
\boxed{\dfrac{4}{9}}
\]
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