Fight Spam with Bayes’ Rule

It might surprise you to know that in 2013, 70.7% of all worldwide emails were spam. Spam emails are unsolicited email that are sent out in bulk. To combat these emails, companies utilize spam filters provided by software companies to block the spam emails from reaching the desired recipient.

One provider, SpamTitan, advertises the following data

  • It blocks 99.9% of all spam email.
  • It blocks 0.03% of all emails that are not spam.

Based on the information above, what is the probability that a delivered email is spam?

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