Finding the Expected Value of Stick Breakage

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SUMMARY

The discussion focuses on calculating the expected value of the lengths of two pieces resulting from breaking a 15-inch stick at a random point. The key approach involves defining a uniform random variable X that represents the break point. The lengths of the two pieces, L and R, are expressed as functions of X, leading to the conclusion that E[L] and E[R] can be derived from E[X]. The expected value of the break point E[X] is crucial for determining the expected lengths of the pieces.

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  • Familiarity with continuous and discrete probability distributions
  • Basic algebra for manipulating equations
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Homework Statement



Suppose that a point is chosen at random on a stick that has length 15 inches, and that the stick is broken into two pieces at that point. Find the expected value of the lengths of the two pieces.


Homework Equations



E(x)=\sumf(x)xdx from -infinity to +infinity (continuous case)
E(x)=\sumf(x)x for all x (discrete case)

The Attempt at a Solution



X1+X2=15

PLEASE HELP!
 
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any ideas?

try starting from a single uniform random variable X, with uniform distribution, representing break distance from one end...
 
Last edited:
Start by defining a random variable X which represents the point where the stick is broken, measured from the left edge. What is E[X]?

Now define two random variables L and R, where L = length of the left piece, and R = length of the right piece.

Express L and R as functions of X. Then use that result to express E[L] and E[R] as functions of E[X].
 

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