CS109 Midterm
Tuesday, Feb 11th, 7pm

The Midterm + Solutions

Here is the distribution color coded with a way of interpreting your score:

The median grade was an 86% (amazing for a hard test!). If you missed some points, we encourage you to look over the answers and understand what went wrong. Make the midterm a learning experience and set yourself up for the final.

Regrade Requests: Humans graded your exam and they might have made a mistake! If they did, we would like to fix it. The deadline to submit regrade requests is Wednesday, Feb 26th at 9am. Requests that often get points back: "my answer was creative, and is numerically equivalent to the accepted solution". Requests that often don't get points back: "I think my approach deserves more partial credit". We reserve the right to regrade the whole exam if you submit a regrade request.

Logistics

The CS109 midterm is a 2-hour, closed book, closed calculator/computer exam. You are, however, allowed to bring 5 pages (front and back) of notes in the exam, formatted in any way you like. Make sure to practice before the exam.

Where to Go

We have reserved three rooms. Which room you go to depends on your last name.

Bishop Auditorium (Lathrop)
Last Name: A through J

STLC 111
Last Name: K through R

Building 420, Room 040
Last Name: S through Z

Alternative Arrangements

If you can not make the CS109 midterm because of an academic conflict (such as having another midterm) we will help you schedule an alternative. Please reach out to us ASAP if that is the case (email Kelly).

Personal Exam Prep New

This year we are trying something new in CS109: Personalized Exam Prep (PEP)!

How does it work? You meet in-person with a TA a week before the midterm for 15 mins. You don't need to prepare or bring anything. The TA gets to know you and, after the session, sends you home with a study guide. Attending PEP is part of your participation grade. You likely will not get your section TA, but it is possible (what is the probability???).

Coverage

The midterm puts special emphasis on the material from the first four problem sets and the first four sections. This includes material in lecture up to and including class on Wed Feburary 5th. In the course reader this corresponds to Part 1, Part 2, Part 3, and Part 4 up through the "Inference" section.

Answer Format

You are going to be solving probability questions by hand. To that extent we are not interested in numberic answers, but rather in formulaic answers. It is fine for your answers to include summations, products, factorials, exponentials, and combinations, unless the question specifically asks for a numeric quantity or closed form. Where numeric answers are required, the use of fractions is fine. You must show your work. Any explanation you provide of how you obtained your answer can potentially allow us to give you partial credit for a problem. For example, describe the distributions and parameter values you used, where appropriate.

What about the Phi table? I am not going to make you look up values from a phi table. Instead you can leave your answer in terms of phi (the CDF of the standard normal). For example $\Phi(\frac{3}{4})$ is a fine final answer. This was not the case in the past so you will see questions which ask for a numeric answer in the practice exams.

Essential Practice

We recommend working through at least one practice midterm exam under realistic conditions (timed) before you take the midterm. Note: You should not expect that a TA will have prepared to answer these problems in office hours (there are far too many for them to prep them all). If you ask about one of this problems on the Ed forum or in office hours please be ready to give the full context, and be aware that the TA might not be able to prioritize them. This is especially true if you ask about them more than a week before the exam.

CS109 Midterm Tuesday, Feb 11th, 7pm