Chapter 8 - Section 8.3 - Measures of Central Tendency - Exercises - Page 576: 20

E(x) = $\frac{3}{2}$

H= head, T = tail P(x=0) → HHH → $(\frac{1}{2})^{3} = \frac{1}{8}$ P(x=1) →THH, HTH, HHT → $3(\frac{1}{2})^{2}(\frac{1}{2}) = \frac{3}{8}$ P(x=2) →TTH, HTT, THT → $3(\frac{1}{2})(\frac{1}{2})^{2} = \frac{3}{8}$ P(x=3) →TTT → $(\frac{1}{2})^{3} = \frac{1}{8}$ E(x) = $0(\frac{1}{8})+1(\frac{3}{8})+2(\frac{3}{8})+3(\frac{1}{8})=\frac{3}{2}$