April 18th, 2014
  • PSET #2 Clarification: For problem #3, when it says the app is wrong 20% of the time, this means that P(app says sunny | weather is rainy) = 0.2.
  • Narek Tovmasyan has been added as a new additional TA for CS109. You can find Narek's office hours and contact information on the staff page.
  • Since we've added a new TA, the was some reshuffling of grader assignments. The tool (below) to look up your grader was updated on April 18th with the new assignments, so please use that to look up your grader.
April 14th, 2014
  • Find out your grader by clicking here
April 10th, 2014
  • Welcome to the new website! Don't worry, you haven't mistyped the URL, this is the new CS109 website. I've been working hard and it's finally ready for you--please take a moment to look around and explore!
April 1st, 2014
  • Problem Set #1 was released on Wednesday, April 2nd. It is due at 12:50pm (at the start of class) on Friday, April 11th.
  • Unless you are an SCPD student, please turn in hardcopies of your problem set submissions. You can turn them in either in class, at Mehran's office (slide them under the door if he's not in) or at your graders office hours (you'll find out who your grader is once you get your first problem set returned).

    Please note that (except for SCPD students) we do not accept submissions via email as we've had too many problems in the past with corrupt files, email message bounces, late delivery, etc.

    SCPD students (only) may submit problem sets via email, via the SCPD courier, or in class.

  • If you are interested in writing-up your problem sets using the LaTex system (this is purely optional), there is a short intoduction to LaTex available as a PDF document, and you can also obtain the original LaTex file that was used to generate that PDF (so you can see an example of LaTex source).

    If you would like to write your solutions for the Problem Sets in LaTex, you might find it useful to start with this LaTex template file for Problem sets.

    An online LaTeX editor and compiler is available at

  • For those of you using LaTex to write your assignments, former CS109 student Joe Delgado has written a nunber of snippets for Latex in Sublime, which he has made available on github. You an find a repo of statistical snippets at: and a repo for more general math snippets at:
March 31st, 2014
  • Welcome to CS109!
  • The first class is Monday, March 31st, 12:50pm-2:05pm in Nvidia Auditorium.
  • Please watch this web site for important class announcements or assignment errata.
  • You might also be interested in the one unit course CS109L: Statistical Programming with R Laboratory.

  • Handouts from class will be available on the handouts page. Any hardcopies remaining after class will be available in the handout bins on the first floor of the Gates building.
  • Staff office hours and locations will be posted on the Course Staff page.

  • The Wall Street Journal published an article entitled New Hiring Formula Values Math Pros talking about how employers are seeking computer scientists with training in statistics and probability. CS109 is specifically mentioned in the article.
  • An article from the New York Times discusses the increasing importance of statistics in computing. The article is entitled For Today's Graduate, Just One Word: Statistics.

Lecturer: Cynthia Lee
Office: Gates 191
Office Hours:
  • Tuesday 1:30-3:30pm
  • Or by appointment.
Professor: Mehran Sahami
Office: Gates 180
Office Hours:
  • Wednesday 2:15-4:15pm
  • Or by appointment.