Fair price of a payout that doubles per head

A fair coin is flipped four times. The game pays 1 dollar, doubled once for every head that appears (no heads pays 1 dollar, two heads pay 4 dollars, four heads pay 16 dollars). What is the fair price of the game, in dollars to four places?

Show hints (2)+
  1. Write the payout as 2H2^H and split it into one factor per flip: 2H=∏i2Xi2^H = \prod_i 2^{X_i}.
  2. Each factor has mean 32\tfrac32; the flips are independent.

Answer

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5.0625 (± 0.001)

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