$A$ coin is biased so that the head is $3$ times as likely to occur as tail. This coin is tossed until a head or three tails occur. If $X$ denotes the number of tosses of the coin,then the mean of $X$ is

  • A
    $\frac{21}{16}$
  • B
    $\frac{81}{64}$
  • C
    $\frac{15}{16}$
  • D
    $\frac{37}{16}$

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Similar Questions

The random variable $X$ has a probability distribution $P(X)$ of the following form,where $k$ is some number:
$P(X) = \begin{cases} k, & \text{if } x=0 \\ 2k, & \text{if } x=1 \\ 3k, & \text{if } x=2 \\ 0, & \text{otherwise} \end{cases}$
Determine the value of $k$.

The cumulative distribution function (c.d.f.) $F(x)$ of a discrete random variable $X$ is given by the following table:
$X$$-3$$-1$$0$$1$$3$$5$$7$$9$
$F(X)$$0.1$$0.3$$0.5$$0.65$$0.75$$0.85$$0.90$$1$

Then,find $P[X=3]$.

$A$ random variable $X$ has the following probability distribution:
$X = x$$1$$2$$3$$4$$5$$6$$7$$8$
$P(X = x)$$0.15$$0.23$$k$$0.10$$0.20$$0.08$$0.07$$0.05$

For the events $E = \{x : x \text{ is a prime number}\}$ and $F = \{x : x < 4\}$,then $P(E \cup F) = $

The probability distribution of a random variable $X$ is given below:
$X=k$$0$$1$$2$$3$$4$
$P(X=k)$$0.1$$0.4$$0.3$$0.2$$0$

The variance of $X$ is:

The probability distribution of a discrete random variable $X$ is given by the following table:
$X = x$$0$$1$$2$$3$$4$
$P(X = x)$$k$$2k$$4k$$2k$$k$

Then the value of $P(X \leq 2)$ is:

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