Which describes a non-uniform probability model?
a) selecting a single card from a deck of cards
b) selecting a ball from 2 purple balls and 2 green balls
c) the chance of an odd or even number from rolling a die
d) selecting a day of the week using only the first letter of that day

My answer is D) Selecting a day of the week using only the first letter of that day

Explanation:
A) The possible outcomes are any single card in the deck
B) The possible outcomes are purple ball and green ball
C) The possible outcomes are odd and even
D) The possible outcomes are M, T, W, T, F **See how letter "T" appeared twice!

The possibility of having T as an outcome is different from others, so it is a non-uniform probability.