5.2 Joint Continuous Distributions Anna Karlin Most slides by Alex - - PowerPoint PPT Presentation

5 2 joint continuous distributions
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5.2 Joint Continuous Distributions Anna Karlin Most slides by Alex - - PowerPoint PPT Presentation

5.2 Joint Continuous Distributions Anna Karlin Most slides by Alex Tsun recap Joint PDFs (Example 1) R R Joint PDFs (Example 1) R R Joint PDFs (Example 1) R R Joint PDFs (Example 1) R R Joint PDFs (Example 1) R R Joint PDFs


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5.2 Joint Continuous Distributions

Anna Karlin Most slides by Alex Tsun

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recap

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Joint PDFs (Example 1)

R R

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Joint PDFs (Example 1)

R R

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Joint PDFs (Example 1)

R R

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Joint PDFs (Example 1)

R R

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Joint PDFs (Example 1)

R R

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Joint PDFs (Example 1)

R R

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Random Picture

probability students Definition of Expectation

The “Normal” Distribution The “Gaussian” Distribution

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Joint PDFs (Example 2)

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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Joint PDFs (Example 2)

1 y=x

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END PIC

Alex Tsun Joshua Fan

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5.3 Law of Total Expectation

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Agenda

  • Conditional Expectation
  • Law of Total Expectation (LTE)
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Conditional Expectation

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E(X|A) = X

x∈Range(X)

xPr(X = x|A)

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Law of Total Expectation

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Law of Total Expectation : Application

System that fails in step i independently with probability p X # steps to fail E(X) ?

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Let A be the event that system fails in first step.

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Law of Total Expectation : Application

System that fails in step i independently with probability p X # steps to fail E(X) ?

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Let A be the event that system fails in first step. E(X) = E(X|A)Pr(A) + E(X|A)Pr(A) = p + (1 + E(X))(1 − p) = 1 + (1 − p)E(X) E(X) = 1 p

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Linearity of expectation applies

To conditional expectation too!! E(X+ Y | A) = E(X | A) + E(Y | A) E(aX + b | A)= a E(X | A) + b

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Law of total Expectation (RV version)

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Problem

The number of people who enter an elevator on the ground floor is a Poisson random variable with mean 10. If there are N floors above the ground floor, and if each person is equally likely to get off at any one of the N floors, independently of where the others get off, compute the expected number of stops that the elevator will make before discharging all the passengers.

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