Pmf Probabilities 977226
1. **Problem Statement:**
A discrete random variable $X$ has a probability mass function (pmf) given by:
$$f(x) = c(x+1), \quad x=0,1,2,3.$$
We need to find:
(a) The constant $c$.
(b) Draw the probability graph and histogram for $f(x)$.
(c) Calculate probabilities:
(i) $P(0 \leq X < 2)$,
(ii) $P(X > 1)$.
2. **Finding the constant $c$:**
Since $f(x)$ is a pmf, the sum of all probabilities must equal 1:
$$\sum_{x=0}^3 f(x) = 1.$$
Substitute $f(x)$:
$$c(0+1) + c(1+1) + c(2+1) + c(3+1) = 1,$$
which simplifies to:
$$c(1 + 2 + 3 + 4) = 1,$$
$$c \times 10 = 1,$$
so
$$c = \frac{1}{10} = 0.1.$$
3. **Probability values:**
Calculate $f(x)$ for each $x$:
- $f(0) = 0.1 \times 1 = 0.1$
- $f(1) = 0.1 \times 2 = 0.2$
- $f(2) = 0.1 \times 3 = 0.3$
- $f(3) = 0.1 \times 4 = 0.4$
4. **Probability graph and histogram:**
- The probability graph is a discrete plot with points at $(0,0.1)$, $(1,0.2)$, $(2,0.3)$, $(3,0.4)$.
- The probability histogram consists of bars at $x=0,1,2,3$ with heights $0.1, 0.2, 0.3, 0.4$ respectively.
5. **Calculating requested probabilities:**
(i) $P(0 \leq X < 2) = P(X=0) + P(X=1) = 0.1 + 0.2 = 0.3.$
(ii) $P(X > 1) = P(X=2) + P(X=3) = 0.3 + 0.4 = 0.7.$
**Final answers:**
- $c = 0.1$
- $P(0 \leq X < 2) = 0.3$
- $P(X > 1) = 0.7$