Mean Variance Bef82B
1. **State the problem:** Given a discrete probability distribution with values of $x$ and their probabilities $P(x)$, we want to calculate the mean $\mu$ and the variance $\sigma^2$.
2. **Recall formulas:**
- Mean: $$\mu = \sum x P(x)$$
- Variance: $$\sigma^2 = \sum (x - \mu)^2 P(x)$$
3. **Calculate the mean $\mu$:**
$$\mu = 0 \times 0.30 + 1 \times 0.28 + 2 \times 0.25 + 3 \times 0.17$$
$$\mu = 0 + 0.28 + 0.50 + 0.51 = 1.29$$
4. **Calculate each $(x - \mu)$:**
- For $x=0$: $0 - 1.29 = -1.29$
- For $x=1$: $1 - 1.29 = -0.29$
- For $x=2$: $2 - 1.29 = 0.71$
- For $x=3$: $3 - 1.29 = 1.71$
5. **Calculate each $(x - \mu)^2$:**
- $(-1.29)^2 = 1.6641$
- $(-0.29)^2 = 0.0841$
- $(0.71)^2 = 0.5041$
- $(1.71)^2 = 2.9241$
6. **Calculate each $(x - \mu)^2 P(x)$:**
- $1.6641 \times 0.30 = 0.49923$
- $0.0841 \times 0.28 = 0.02355$
- $0.5041 \times 0.25 = 0.12603$
- $2.9241 \times 0.17 = 0.49710$
7. **Sum these to find variance $\sigma^2$:**
$$\sigma^2 = 0.49923 + 0.02355 + 0.12603 + 0.49710 = 1.14591$$
**Final answers:**
- Mean $\mu = 1.29$
- Variance $\sigma^2 = 1.15$ (rounded to two decimals)