diff --git a/source/main.ptx b/source/main.ptx
index 05b796d..0ea7f5f 100644
--- a/source/main.ptx
+++ b/source/main.ptx
@@ -28,6 +28,7 @@
       <xi:include href="./notes/1-22.ptx" />
       <xi:include href="./notes/1-27.ptx" />
       <xi:include href="./notes/1-29.ptx" />
+      <xi:include href="./notes/2-3.ptx" />
     </chapter>
 
     <chapter xml:id="quizzes">
@@ -44,5 +45,14 @@
       <xi:include href="./recitations/calculus-review.ptx"/>
      
     </chapter>
+
+    <chapter xml:id="review">
+      <title>Exam Review</title>
+
+      <xi:include href="./review/Exam-1-Review.ptx"/>
+     
+    </chapter>
+
+
   </book>
 </pretext>
\ No newline at end of file
diff --git a/source/notes/2-3.ptx b/source/notes/2-3.ptx
new file mode 100644
index 0000000..288fe9c
--- /dev/null
+++ b/source/notes/2-3.ptx
@@ -0,0 +1,41 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<section xml:id="notes-02-03">
+  <title>Tuesday, Feb 3</title>
+
+  <introduction>
+    <p>
+      This is an outline of the topics we covered in class.
+      These notes are <em>not</em> a substitute for your own note-taking.
+      I highly recommend that you take your own notes during class.
+      If you ever miss a class for any reason, reach out to another student in class to get a copy of their notes.
+    </p>
+  </introduction>
+
+
+  <subsection>
+    <title>Variance</title>
+
+    <p>
+      Question: How spread out are <m>X</m> values? One answer we might try is to measure the average distance from the average value:
+      <md>
+        <mrow> \E\left[|X - \E(X)|\right] </mrow>
+      </md>
+      To simplify notation, we'll write <m>\mu = \E(X)</m>.
+      Also, it's often usefull to square a term rather than take absolute value when we want to ensure a positive output, so we'll define...
+    </p>
+
+    <definition xml:id="def-variance">
+      <statement>
+        <p>
+          Let <m>X</m> be a random variable with <m>\E(X) = \mu</m>.
+          The <term>variance</term> of <m>X</m> is:
+          <md>
+            <mrow> \sigma^2 = \Var(x) = \E\left[ (X - \mu)^2\right] </mrow>
+          </md>
+          <m>\sigma = \sqrt{\Var(X)}</m> is called the <term>standard deviation</term>.
+        </p>
+      </statement>
+    </definition>
+  </subsection>
+</section>
\ No newline at end of file
diff --git a/source/quizzes/quiz-02.ptx b/source/quizzes/quiz-02.ptx
index 16a4d1f..c4fbf32 100644
--- a/source/quizzes/quiz-02.ptx
+++ b/source/quizzes/quiz-02.ptx
@@ -140,7 +140,16 @@
 
         <solution>
           <p>
-            <m>\Pr(X = 2, Y = 0) = 0.2 </m>, and <m> \Pr(X = 2)\Pr(Y = 0) = (0.4)(0.25) = 0.1</m>. Since <m>0.2 \neq 0.1</m>, <m>X</m> and <m>Y</m> are not independent.
+            Checking each cell in the table:
+            <md>
+              <mrow> \Pr(X = 0, Y = 0) \amp = 0.1 = (0.4)(0.25) = \Pr(X = 0)\Pr(Y = 0) </mrow>
+              <mrow> \Pr(X = 1, Y = 0) \amp = 0.05 = (0.2)(0.25) = \Pr(X = 1)\Pr(Y = 0) </mrow>
+              <mrow> \Pr(X = 2, Y = 0) \amp = 0.1 = (0.4)(0.25) = \Pr(X = 2)\Pr(Y = 0) </mrow>
+              <mrow> \Pr(X = 0, Y = 1) \amp = 0.3 = (0.4)(0.75) = \Pr(X = 0)\Pr(Y = 1) </mrow>
+              <mrow> \Pr(X = 1, Y = 1) \amp = 0.15 = (0.2)(0.75) = \Pr(X = 1)\Pr(Y = 1) </mrow>
+              <mrow> \Pr(X = 2, Y = 1) \amp = 0.3 = (0.4)(0.75) = \Pr(X = 2)\Pr(Y = 1) </mrow>
+            </md>
+            So <m>X, Y</m> are independent.
           </p>
         </solution>
       </task>
diff --git a/source/review/Exam-1-Review.ptx b/source/review/Exam-1-Review.ptx
new file mode 100644
index 0000000..aed9e5f
--- /dev/null
+++ b/source/review/Exam-1-Review.ptx
@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<section xml:id="Exam-1-Review">
+  <title>Exam 1 Review</title>
+
+  <introduction>
+    <p>
+      Use the following problems to prepare for the exam.
+      There will be in-class review on Thursday, February 12.
+      Your recitation this week will also be exam review.
+    </p>
+  </introduction>
+
+
+  <subsection>
+    <title>Allowed Materials</title>
+
+    <p>
+      You will be allowed to use a scientific calculator (<em>not</em> a graphing calculator, <em>not</em> a calculator app on your phone).
+      You may not share a calculator with another student; you must use your own calculator.
+    </p>
+
+    <p>
+      You may bring a standard 3 in x 5 in index card with prepared notes.
+      You may use both sides of the notecard.
+      You must put your full name in the top right corner of the card, and turn it in along with your exam.
+    </p>
+  </subsection>
+
+  <exercises>
+  <exercise>
+    <p>
+    </p>
+  </exercise>
+  </exercises>
+</section>
\ No newline at end of file