-This is a short description of the ID method.
+The serial interval (SI) is NOT one of the estimators.
+
+<p>The SI is a parameter required by all of the estimators, and can also be estimated by the WP method.</p>
+
+<p>The SI is defined as the average time between successive infections in a chain of transmission i.e., the time between the infection of an infected and their subsequent transmissions. </p>
+
+<P> Make the tab a different shade (light gray) and then this won't have parameters. It will let us not have to explain SI every single time. We'll expand the description later.</p>