Store discounts. Many stores run “secret sales”:

Shoppers receive cards that determine how large a discount they get, but the percentage is revealed by scratching off that black stuff (what is that?) only after the purchase has been totaled at the cash register. The store is required to reveal (in the fine print) the distribution of discounts available. Are each of these probability assignments plausible?

Why or why not?

Probabilities of ... 10% off 20% off 30% off 50% off a) 0.20 0.20 0.20 0.20 b) 0.50 0.30 0.20 0.10 c) 0.80 0.10 0.05 0.05 d) 0.75 0.25 0.25 -0.25 e) 1.00 0 0 0