Question 1190697
**1. MTRCB Commercials**

*   **Mean:** The mean (or expected value) is calculated by multiplying each value of x by its probability and summing the results:

    Mean = (10 * 0.15) + (11 * 0.35) + (12 * 0.30) + (13 * 0.20) = 11.55

*   **Variance:** The variance measures the spread of the distribution.  It's calculated as the average of the squared differences from the mean:

    Variance = [(10-11.55)² * 0.15] + [(11-11.55)² * 0.35] + [(12-11.55)² * 0.30] + [(13-11.55)² * 0.20] ≈ 0.9475

*   **Standard Deviation:** The standard deviation is the square root of the variance:

    Standard Deviation = √0.9475 ≈ 0.973

**2. RFS Electronics Iphones**

*   **Expected Number of Iphones (Mean):**  This is calculated the same way as the mean in the previous problem:

    Expected Number = (0 * 0.05) + (1 * 0.10) + (2 * 0.12) + (3 * 0.15) + (4 * 0.18) + (5 * 0.40) = 3.51

*   **Variance:**  Calculate the variance using the same method as above:

    Variance = [(0-3.51)² * 0.05] + [(1-3.51)² * 0.10] + [(2-3.51)² * 0.12] + [(3-3.51)² * 0.15] + [(4-3.51)² * 0.18] + [(5-3.51)² * 0.40] ≈ 2.4899

*   **Standard Deviation:**

    Standard Deviation = √2.4899 ≈ 1.578