Question

In a large collection of real SMS text messages from particular cellphone users, 13.40% of messages are identified as spam. Of all spam messages 17.0% contain both the word "free" and the word "text" ("txt") For example, "Congrats!! You have been selected to receive a free camera phone, txt ******* to claim your prize." Of all non=spam messages, 6% contain both the words "free" and the word "text" (or "txt"). Given that a message contains both the word "free" and the word "text" (or "txt"), what is the probability that it is spam?

Answer 1

30