ما معنى Trading game؟

Example 6.4 (The three-card market)

Cards count 1 (ace) to 13 (king), four of each, 52 in all. The sum of three cards drawn without replacement has mean $3 \times 7 = 21$ and variance $3 \times 14 \times \tfrac{49}{51} \approx 40.4$ (each card has variance $(13^2 - 1)/12 = 14$, reduced by the finite-population factor), so a standard deviation of about 6.35; an exact enumeration puts 90% of the outcomes between 10 and 32. A market of 19 at 23 is centred and about a third of a standard deviation wide on each side. When a card is shown, the fair value becomes that card plus twice the mean of the 51 remaining cards: a king moves it to $13 + 2 \times 351/51 \approx 26.76$. Figure 6.1 follows one game’s fair value as its cards appear.