The problem asks to construct the cumulative distribution function (CDF), $F(x)$, for a discrete random variable $X$. Also, it mentions constructing a graph. The given probability distribution is defined as: $P(X = 2) = 0.3$ $P(X = 4) = 0.1$ $P(X = 5) = 0.2$ $P(X = 6) = 0.4$ The CDF is given by $F(x) = P(X \le x)$.

Probability and StatisticsCumulative Distribution FunctionCDFDiscrete Random VariableProbability DistributionStep Function
2025/4/8

1. Problem Description

The problem asks to construct the cumulative distribution function (CDF), F(x)F(x), for a discrete random variable XX. Also, it mentions constructing a graph. The given probability distribution is defined as:
P(X=2)=0.3P(X = 2) = 0.3
P(X=4)=0.1P(X = 4) = 0.1
P(X=5)=0.2P(X = 5) = 0.2
P(X=6)=0.4P(X = 6) = 0.4
The CDF is given by F(x)=P(Xx)F(x) = P(X \le x).

2. Solution Steps

First, we calculate the CDF for each value of xx:
For x<2x < 2, F(x)=P(Xx)=0F(x) = P(X \le x) = 0
For 2x<42 \le x < 4, F(x)=P(Xx)=P(X=2)=0.3F(x) = P(X \le x) = P(X = 2) = 0.3
For 4x<54 \le x < 5, F(x)=P(Xx)=P(X=2)+P(X=4)=0.3+0.1=0.4F(x) = P(X \le x) = P(X = 2) + P(X = 4) = 0.3 + 0.1 = 0.4
For 5x<65 \le x < 6, F(x)=P(Xx)=P(X=2)+P(X=4)+P(X=5)=0.3+0.1+0.2=0.6F(x) = P(X \le x) = P(X = 2) + P(X = 4) + P(X = 5) = 0.3 + 0.1 + 0.2 = 0.6
For x6x \ge 6, F(x)=P(Xx)=P(X=2)+P(X=4)+P(X=5)+P(X=6)=0.3+0.1+0.2+0.4=1.0F(x) = P(X \le x) = P(X = 2) + P(X = 4) + P(X = 5) + P(X = 6) = 0.3 + 0.1 + 0.2 + 0.4 = 1.0
Therefore, the CDF F(x)F(x) is a step function:
$F(x) = \begin{cases}
0, & x < 2 \\
0.3, & 2 \le x < 4 \\
0.4, & 4 \le x < 5 \\
0.6, & 5 \le x < 6 \\
1.0, & x \ge 6
\end{cases}$

3. Final Answer

The cumulative distribution function is:
$F(x) = \begin{cases}
0, & x < 2 \\
0.3, & 2 \le x < 4 \\
0.4, & 4 \le x < 5 \\
0.6, & 5 \le x < 6 \\
1.0, & x \ge 6
\end{cases}$

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