There are 3 boys and 2 girls at a party. Three party-goers are selected at random to go on a root-beer run. Let W denote the number of girls in the group of three that go on the root-beer run. Compute the expected number of girls who go on the root-beer run, E[W].

A First Course in Probability (10th Edition)
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ISBN:9780134753119
Author:Sheldon Ross
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Chapter1: Combinatorial Analysis
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There are 3 boys and 2 girls at a party.
Three party-goers are selected at random to
go on a root-beer run. Let W denote the
number of girls in the group of three that go
on the root-beer run.
Compute the expected number of girls who
go on the root-beer run, E[W].
Transcribed Image Text:There are 3 boys and 2 girls at a party. Three party-goers are selected at random to go on a root-beer run. Let W denote the number of girls in the group of three that go on the root-beer run. Compute the expected number of girls who go on the root-beer run, E[W].
Expert Solution
Step 1

There are 3 boys and 2 girls at the party.

Three party-goers are selected at random to go on the root beer run.

An event W is a number of girls in a group of three that go on the root beer run.

The expected value formula is as follows

E[W]=i=1nwiP(W=wi)

The combination formula is as follows.

Cx=n!(n-x)!x!n

The factorial is as follows.

n!=n×(n-1)×(n-2)×...×1

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