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Let Xbe such thatP{X=1}=p=1-P{X=-1}

Find c≠1such that EcX=1.

Short Answer

Expert verified

The two possible values of c are p and 1p-1.

Step by step solution

01

Given information

Given in the question that,

P{X=1}=p=1-P{X=-1}.

02

Calculation

Observe that random variable Xassumes only two values with positive probability. We have that

P(X=1)=p

P(X=-1)=1-p

Using the theorem about the expectation of a function of a random variable,

We have that

1=EcX=c×p+1c(1-p)

Multiply both sides with c, we end up with an equation

pc2-c+(1-p)=0.

03

Solution

Two solutions are,

c1,2=1±1-4p(1-p)2p

Observe that the term under the root is equal to (2p-1)2, so we have

c1,2=1±|2p-1|2p

Therefore, we get that we have two answers

c1=1,c2=1-pp.

04

Final answer

There exist two possible values of c. They are p and 1p-1.

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In the game of Two-Finger Morra, 2players show 1or 2fingers and simultaneously guess the number of fingers their opponent will show. If only one of the players guesses correctly, he wins an amount (in dollars) equal to the sum of the fingers shown by him and his opponent. If both players guess correctly or if neither guesses correctly, then no money is exchanged. Consider a specified player, and denote by X the amount of money he wins in a single game of Two-Finger Morra.

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