In a meeting, 70% of the members favour and 30% oppose a certain proposal. A member is selected at random and we take $X = 0$ if he opposed, and $X= 1$ if he is in favour. Then, $E (X)$ is:
Answer & explanation
Correct answer: option 1
$F$ → favour
$\overline F$ → oppose
$P(F) = 70\%=\frac{7}{10}$ $X=1$
$P(\overline F) = 30\%=\frac{3}{10}$ $X=0$
So, $E(X) = 0×\frac{3}{10}+1×\frac{7}{10}=\frac{7}{10}$