Introduction to Probability

Lecture

• Slides
• In-class exercises

Probability Rules

• Probability of mutually exclusive events A or B
  • $P[A\ or\ B] = P[A] + P[B]$

• Probability of not mutually exclusive events A or B
  • $P[A\ or\ B] = P[A] + P[B] - P[A\ and\ B]$

• Probability of independent events A and B
  • $P[A\ and\ B] = P[A]\ *\ P[B]$

• Probability of dependent events A and B

  • $P[A\ and\ B] = P[B\vert A]\ *\ P[A]$

  • $P[B\ and\ A] = P[A\vert B]\ *\ P[B]$

• Together, the above probabilities reveal Bayes Theorem
  • $P[B\vert A] = \large{\frac{P[A\vert B]\ *\ P[B]}{P[A]}}$

R lab

Most R materials are available in slides. In addition, the function na.omit() will remove all rows with NA’s from a data frame.