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Random Variable and Mathematical Expectation 5 Mark Creative Question Paper With Answer Key

12th Standard

    Reg.No. :
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Business Maths

Time : 01:00:00 Hrs
Total Marks : 75

     5 Marks 

    15 x 5 = 75
  1. A discrete random variable X has the following probability distribution.

    x 1 2 3 4 5 6 7
    P(X) c 2c 2c 3c c2 2c2 7c2+c

    Find the value of e. Also, find the mean of the distribution.

  2. The probability distribution of a random variation X is given below.

    X 0 1 2 3 4
    P(X) 0.1 0.25 0.3 0.2 0.15

    Find
    (i) V(X)
    ii) V\((\frac{X}{2})\)

  3. The probability distribution of the discrete random variables X and Y are given below

    X 0 1 2 3
    P(X) \(\frac{1}{5}\) \(\frac{2}{5}\) \(\frac{1}{5}\) \(\frac{1}{5}\)
    Y 0 1 2 3
    P(Y) \(\frac{1}{5}\) \(\frac{3}{10}\) \(\frac{2}{5}\) \(\frac{1}{10}\)

    Prove that E(Y2) = 2E(X).

  4. The random variable X tan take only the values 0,1,2. Given that P(X = 0) = P(X = 1) = P and E(X2) = E(X), find the value of p.

  5. The probability distribution of a random variable X is

    X 1 2 4 2A 3A 5A
    P(X) \(\frac{1}{2}\) \(\frac{1}{5}\) \(\frac{3}{25}\) \(\frac{1}{10}\) \(\frac{1}{25}\) \(\frac{1}{25}\)

    Calculate
    (i) A if E(X) = 2.94
    (ii) V(X)

  6. Let X denote the number of hours you study during a randomly selected school day. The probability that X can take the value X has the following form, where k is some unknown constant \(p(X=x)= \begin{cases}0.1 & \text { if } x=0 \\ k x & \text { if } x=1 \text { or } 2 \\ k(5-x) & \text { if } x=3 \text { or } 4 \\ 0 & \text { otherwise }\end{cases}\)
    (i) Find the value of k 
    (ii) What is the probability that you study atleast 2 hours? 
    (iii) Exactly 2 hours
    (iv) At most 2 hours

  7. Two numbers are selected at random (without replacement) from the first six positive integers. Let X denote the larger of two numbers obtained. Find E(X) and var (X).

  8. Find the probability distribution of the number ofsuccess in 2 tosses of a die, where a success in defined as "getting a number greater than 4". Also find the mean and variance of the distribution

  9. A fair coin is tossed until a head or five tails occur. If X denotes the number of tosses of the coin, find mean of X

  10. A random variable X has the following probability mass function 

    x 0 1 2 3 4 5 6
    P(X=x) k 3k 5k 7k 9k 11k 13k

    (i) Find k
    (ii) Evaluate \(\mathbf{P}(x<4), P(x \geq 5), \quad \mathrm{P}(3<x \leq 6)\)
    (iii) What is the smallest value of x for which \(\mathrm{P}(X \leq x)>\frac{1}{2}\)

  11. A continuous random variable X has p.d.f \(f(x)=3 x^{2}, \ 0 \leq x \leq 1\). Find a and b such that 
    (i) \(\mathrm{P}(x \leq \mathrm{a})=\mathrm{P}(x>\mathrm{a})\)
    (ii) \( \mathrm{P}(x>\mathrm{b})=0.05\)

  12. If the probability density function of a random variable is given by \(f(x)= \begin{cases}k\left(1-x^{2}\right) & 0<x<1 \\ 0 & \text { elsewhere }\end{cases}\)
    (i) Find k
    (ii) The distribution function of the random variable

  13. For the p.d.f \(f(x)=\left\{\begin{array}{lc} \operatorname{Cx}(1-x)^{3}, & 0<x<1 \\ 0, & \text { elsewhere } \end{array}\right.\) 
    (i) the constant C
    \(\text {(ii) } \mathrm{P}\left(x<\frac{1}{2}\right)\)

  14. A continuous random variable has the following p.d.f, \(f(x)= \begin{cases}k x^{2}, & 0 \leq x \leq 10 \\ 0, & \text { otherwise }\end{cases}\) find k and evaluate
    \((i)\ \mathrm{P}(0.2 \leq x \leq 0.5) \)
    (ii) \( \mathrm{P}(x \leq 3)\)

  15. Let X be a continuous random variable with \(\text { p.d.f } f(x)= \begin{cases}a x & 0 \leq x \leq 1 \\ a & 1 \leq x \leq 2 \\ -a x+3 a & 2 \leq x \leq 3 \\ 0 & \text { otherwise }\end{cases}\)
    (i) Determine the constant a
    (ii) Compute \(\mathrm{P}(x \leq 1.5)\)

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