8.8. On each bet, a gambler loses 1 with probability.7, loses 2with probability .2, or wins 10with probability .1. Approximate the probability that the gambler will be losing after his first 100 bets.

Short Answer

Expert verified

The probability is .6103.

Step by step solution

01

Given information

A gambler loses 1with probability .7, loses 2 with probability .2, or wins 10 with probability .1.

02

Explanation

Let Xidenotes the gambler's winnings on ith bet. Then, discrete random variable, takes the values, -1,-2and 10.

Probabilities:

PXi=-1=.7,PXi=-2=.2,

And, PXi=10=.1
Hence, the value ofXi is:
μ=E[X]=(-1)(.7)+(-2)(.2)+10(.1)=-.1EX2=(-1)2(.7)+(-2)2(.2)+102(.1)=11.5
The variance ofXi is
σ2=VarXi=11.5-(-.1)2=11.49

03

Explanation

Let, gambler's first100 bets:
X=X1+X2++X100
The probability that the gambler will be losing after his first100 bets is:
P{X<0}
Using the central limit theorem:
P{X<0}=PX-100μ10σ<(0-.5)-100μ10σΦ-.5-100μ10σ=Φ-.5-100(-.1)1011.49=Φ(.28)=.6103

Hence, the probability is .6103

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