Mean and variance of discrete distributions

Mean and variance of discrete distributions Quiz

Spec 1.1 · Edexcel A-Level Further Maths: Quiz

Studying this course? Keep your progress in one place.

Pick an answer for each. Quizzes never use energy.

5 questions, one answer each

Each answer is checked as you go, with why.

See all 5 questions

  1. 1. P(X=1)=0.5P(X=1)=0.5, P(X=2)=0.3P(X=2)=0.3, P(X=3)=0.2P(X=3)=0.2. Find E(X)E(X).

    • A. 22
    • B. 3.53.5
    • C. 1.71.7
    • D. 0.610.61

  2. 2. For the same distribution, E(X2)=3.5E(X^2)=3.5. Find Var(X)\text{Var}(X).

    • A. 3.53.5
    • B. 0.610.61
    • C. 1.71.7
    • D. 0.780.78

  3. 3. For the same distribution, find E(2X2−1)E(2X^2-1).

    • A. 55
    • B. 2.42.4
    • C. 4.784.78
    • D. 66

  4. 4. P(X=x)=kx2P(X=x)=kx^2 for x=1,2,3x=1,2,3. Find kk.

    • A. 114\frac1{14}
    • B. 16\frac16
    • C. 19\frac19
    • D. 13\frac13

  5. 5. A model has mean 33 and variance 11. Data have mean 3.13.1 and variance 4.24.2. Which comment is best?

    • A. The model is suitable because the means are almost equal.
    • B. The model is suitable because the variances are both small.
    • C. The means agree but the model's variance is far smaller than the data's, so it may be unsuitable.
    • D. The model is unsuitable because the means are not exactly equal.

Quiz