Chengwei LEI, Ph.D.    Associate Professor

Department of Computer and Electrical Engineering and Computer Science
California State University, Bakersfield

 

Probability Basics



Basics

 



 

The box of dice:

  • 99% fair, 1% loaded (50% at six)
  • randomly pick a die and roll
  • If we get 3 six in a row, what’s the chance that the die is loaded?
  • If we get 5 six in a row, what’s the chance that the die is loaded?

Bayes Theorem

 

 

Am I dying ?:

  • There is a rare deadly disease is present in the population at 1 in 100,000
  • A test for this disease will report positive for 99.5% of people with disease, and negative 99.9% of time for those without.
  • One day, I took this test, and got a Postivite result. Am I dying?

Bayes Disease