alleryThe **cumulative distribution function (c.d.f.)** $F(x)$ of a discrete random variable is:
A$F(x) = P[X = x]$
B$F(x) = 1 - p$
C$F(x) = P[X \leq x] = \sum_{x_i \leq x} p_i$
D$F(x) = P[X > x]$
Answer & Solution
Correct answer: C. $F(x) = P[X \leq x] = \sum_{x_i \leq x} p_i$
c.d.f.
accumulates: $F(x) = P[X \leq x] = \sum_{x_i \leq x} p_i$.
It is non-decreasing, starts at 0 (for $x < \min$), reaches 1 (at $x \geq \max$).
For discrete RV it's a step function.
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