3. You have an urn with 30 red balls and 60 other balls that are either black or yellow. You don’t know the ratio of black to yellow, only that the total of black and yellow is 60. There is a prize for winning and no penalty for losing. Choose which wager you would prefer:

a. You get $100 if you draw a red ball.

b. You get $100 if you draw a black ball.

gamble

(b) to gamble (a), by similar logic you should prefer gamble

(d) to gamble (c). But in actual surveys, most people strictly prefer gamble

(a) to gamble (b), and gamble

(d) to gamble (c). The logic that informs one decision breaks down for the other.
The idea of the ambiguity effect is that people prefer known risks over unknown risks, regardless of other factors. Choosing gamble

(a) over gamble

(b) is a preference for knowing the number of red balls, even though the number of black balls might be greater. Choosing gamble (d)
over gamble

(c) is a preference for knowing that the sum of black and yellow balls is 60, even if the sum of red and yellow might be greater.