Lecture12_Chapter3

# Lecture12_Chapter3 - Lecture 12 Chapter 3 Monday October...

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Lecture 12 – Chapter 3 Monday, October 6 th

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Example ± In State College there are 10000 families. I asked them how many kids they have and I get the following answers: ² 0 kids: 900 families ² 1 kid: 1700 families ² 2 kids: 4000 families ² 3 kids: 2100 families ² 4 kids: 700 families ² 5 kids: 400 families ² 6 kids: 200 families
Question ± If I choose a family at random, how many kids I expect it to have? ± How did I calculate this value?

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Expected value ± If X is a random variable with a set of all possible values denoted with D and pmf p(x). The expected value or mean value of X is: () ( ) X xD E Xx p x μ ==
Example ± I roll a die once. What is the expected outcome of the number I will see.

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Example ± Let say the probability of a pregnant woman to give a birth to a boy is p. ± What is the expected number of X = the child is a boy? ± What is the expected number of Y = the child is a girl? ± How many boys I expect to see if I observe 100 births?
Expected value of a function ± If the random variable X has a set of

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## This note was uploaded on 09/23/2009 for the course STAT 318 taught by Professor Staff during the Fall '08 term at Penn State.

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Lecture12_Chapter3 - Lecture 12 Chapter 3 Monday October...

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