A box holds red cards numbered 1 to 3 and blue cards numbered 1 to 5. What is the probability the card is even given that it is blue?

1. The box holds eight cards in all, three red and five blue. 2. Conditioning on blue reduces the sample space to the five blue cards. 3. Two of those blue cards carry even numbers, namely 2 and 4. 4. Two out of five gives a probability of 2/5. 5. A value of 3/8 is the plain probability of drawing an even card from all eight, which ignores the condition. 6. A value of 2/3 answers the reverse conditional, the chance of blue given that the card is even. _Source: OpenStax Introductory Business Statistics (CC BY 4.0), Ch 3 "Probability Topics", section 3.2 Independent and Mutually Exclusive Events_