AN EVAR ANALOGY
The following analogy helps explain how eVars work as well as their relationship with events (already discussed at length). An event is compared to a wicket or hoop in a croquet game.

Wicket are just something you pass a ball through. They don’t contain anything themselves, but you can easily count how many times a ball passes through. Events are simply conversion counters.

On the other hand, a conversion variable does contain information, whether it is a pre-name variable (e.g., s.campaign) or a custom eVar (e.g., Internal Search Term). Conversion variable use persistent cookies to hold information for a time (the duration of which is set in the Conversion Variable settings in the Admin console). In addition to the wicket (the event), you also have a croquet ball, which represents the visitor “rolling” around the Web and to your site. You hope that ball (visitor) will go through the “wicket” and complete a conversion. To go a little further, imagine that the croquet ball is covered with Velcro.

Let’s say this visitor comes to your site by clicking on a blue banner ad you have placed on a Yahoo page, which is assigned a tracking code named “yahoo:blue”. Because tracking codes in Site Catalyst are capture in a conversion variable called s.campaign, that value “sticks” to the Velcro-covered ball (is stored in a persistent cookie). On a subsequent page, the visitor clicks on a “20% off” internal promotion, which is captured in one of your custom conversion variables: eVar3. That “2-% off” value also “sticks” to the ball. A few pages later, the visitor decided to subscribe to the monthly edition of your newsletter. You capture Subscription Type in eVar5. This value also sticks to the ball, and now this visitor is rolling around your site with several values stick to him. Remember that Events, represented here by a wicket, are simply conversion counters used to count the conversion activities on your site, toward which you are trying to drive visitors. A conversion Event could be a purchase, signup, a request for information, a subscription, or virtually any other action the visitor takes (as defined by you for your site).

The Velcro ball represents the visitor and holds all the information captured in persistent conversion variables, whether they are custom eVars pr pre-named standard variables. For example, say Event is a subscription. When a visitor “rolls through” a subscription, the Event simply says, “Ding! A subscription happened. And when it did, it was to someone who came in from the Yahoo blue banner, clicked on the 20% off promotion, and chose a monthly subscription.” All conversion variable values in the cookie-the Velcro ball-are automatically credited the subscription.

The conversion values show up as line items in Site Catalyst reports based upon that variable. You may remember that you can keep track of banner ads in the s.campaign variable, which fills the Tracking Codes report. When you run a Tracking Codes report, somewhere in the list of all Tracking Codes, you will see that Yahoo blue banner, ranked by the Event, which is the number of subscriptions. You can see which Internal Promotions were most effective in driving subscriptions by running the report based on custom evar3 called Internal Promotions. All of your internal promotions will be listed in the report and ranked once again by the Event, Subscriptions. In like manner, you can see all your Subscription Types (eVar5), ranked by the Event, Subscriptions.

COMMON USES OF EVARS
Some of the common use of eVars include:

  • Internal Search Terms.
  • A/B Testing.
  • Campaign/Promotion tracking.
  • Merchandising Categories.
A brief discussion or each of these uses is outline in the following sections.