Continuous Random Variables (VCE SSCE Mathematical Methods): Flashcards

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Continuous Random Variables
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Continuous random variable definition

Variable that can take any value within a specific interval

Continuous vs discrete random variables

Continuous: any value in range; Discrete: specific separated values

Point probability for continuous random variable

Pr(X=x)=0\Pr(X = x) = 0 for all xx

Probability density function (PDF)

Function representing probability distribution of continuous variable

First property of PDF

f(x)0f(x) \geq 0 for all xx (always non-negative)

Second property of PDF

f(x)dx=1\int_{-\infty}^{\infty} f(x) \, dx = 1 (total area equals 1)

How probabilities are represented for continuous variables

As areas under the PDF curve

Formula for Pr(a<X<b)\Pr(a < X < b) using PDF

Pr(a<X<b)=abf(x)dx\Pr(a < X < b) = \int_a^b f(x) \, dx

Can PDF values be greater than 1?

Yes, f(x)f(x) values are not probabilities themselves

Interval probability equivalence for continuous XX

Pr(a<X<b)=Pr(aXb)\Pr(a < X < b) = \Pr(a \leq X \leq b) (endpoints don't matter)

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