The probability distribution of the discrete random variable $X$ is shown in the table below. $x$ $-3$ $-1$ 0 4 --- --- --- --- --- $\text{P}(X = x)$ $a$ $b$ 0.15 0.4 Given that $\text{E}(X) = 0.75$, find the values of $a$ and $b$.

Mathematics 9709/61 — May/June 2010

Cambridge AS Level · Probability & Statistics 1 (S1) · worked solutions for every part, with the mark scheme

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Topics Discrete Random Variables · Representation of Data · The Normal Distribution · Permutations and Combinations · Probability

Q14MDiscrete Random VariablesFree sample

The probability distribution of the discrete random variable $X$ is shown in the table below.

$x$	$-3$	$-1$	0	4
$\text{P}(X = x)$	$a$	$b$	0.15	0.4

Given that $\text{E}(X) = 0.75$ , find the values of $a$ and $b$ .

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