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Random Variable and Mathematical Expectation Book Back Questions

12th Standard

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Business Maths

Time : 00:45:00 Hrs
Total Marks : 30
    5 x 1 = 5
  1. Value which is obtained by multiplying possible values of random variable with probability of occurrence and is equal to weighted average is called ________.

    (a)

    Discrete value

    (b)

    Weighted value

    (c)

    Expected value

    (d)

    Cumulative value

  2. Probability which explains x is equal to or less than particular value is classified as ________.

    (a)

    discrete probability

    (b)

    cumulative probability

    (c)

    marginal probability

    (d)

    continuous probability

  3. If X is a discrete random variable and p(x) is the probability of X, then the expected value of this random variable is equal to ________.

    (a)

    \(\sum { f(x) } \)

    (b)

    \(\sum[x+f(x)]\)

    (c)

    \(\sum { f(x)+x } \)

    (d)

    \(\sum { xp(x) } \)

  4. Which of the following is not possible in probability distribution?

    (a)

    \(\sum { p(x)\ge 0 } \)

    (b)

    \(\sum { p(x)=1 } \)

    (c)

    \(\sum { xp(x)=2 } \)

    (d)

    \(p(x)=-0.5\)

  5. A discrete probability distribution may be represented by ________.

    (a)

    table

    (b)

    graph

    (c)

    mathematical equation

    (d)

    all of these

  6. 3 x 2 = 6
  7. Construct cumulative distribution function for the given probability distribution.

    X 0 1 2 3
    P(X = x) 0.3 0.2 0.4 0.1
  8. The discrete random variable X has the probability function

    X 1 2 3 4
    P(X=x)  k   2k  3k 4k

    Show that k = 0.1.

  9. Two coins are tossed simultaneously. Getting a head is termed as success. Find the probability distribution of the number of successes.

  10. 3 x 3 = 9
  11. \(\text { If } \ p(x) \ = \begin{cases}\frac{x}{20}, & x=0,1,2,3,4,5 \\ 0, & \text { otherwise }\end{cases}\)
    Find
    (i) P(X<3) and 
    (ii) P(2\(\leq\)4)

  12. A coin is tossed thrice. Let X be the number of observed heads. Find the cumulative distribution function of X.

  13. A continuous random variable X has p.d.f
    f(x) = 5x4, 0\(\le\)x\(\le\)
    Find a1 and a2 such that
    i) P[X\(\le\)a1] = P[X>a1]   
    ii) P[X>a2] = 0.05

  14. 2 x 5 = 10
  15. Determine the mean and variance of a discrete random variable, given its distribution as follows.

    X = x 1 2 3 4 5 6
    Fx(x) \(\frac{1}{6}\) \(\frac{2}{6}\) \(\frac{3}{6}\) \(\frac{4}{6}\) \(\frac{5}{6}\) 1
  16. A commuter train arrives punctually at a station every 25 minutes. Each morning, a commuter leaves his house and casually walks to the train station. Let X denote the amount of time, in minutes, that commuter waits for the train from the time he reaches the train station. It is known that the probability density function of X is
    \(f(x)= \begin{cases}\frac{1}{25}, \text { for } & 0 < x < 25 \\ 0, & \text { otherwise }\end{cases}\)
    Obtain and interpret the expected value of the random variable X.

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