I have a processing rule in the Marketing Channel set up that is defined as "query string parameter icmp contains appen". This query string parameter (icmp) is collected in a dimension called Internal Campaign ID. When I break down the channel corresponding to that processing rule by the dimension Internal Campaign ID and use Visits as a metric, I have a number of visits that are classified as Unspecified. How is this possible, as the rule should only include visits that have entered the site with that query string parameter? Also, which metric is the preferred one to use in Marketing Channel to see the channel distribution of the incoming traffic?
@Annelio I would advice using Marketing Channel instance metric to see how many times a marketing channel was defined in an image request (either s.t() and s.tl() image calls).
From the screenshot, it looks like eVar32 is not getting captured as expected from the URL for 'SEB Mobile Apps' marketing channel, that a visitor uses to navigate to your website. I will recommend pulling a data feed report and reviewing the pageurl column to see what is actually being captured in that visit.
You should never breakdown the Marketing Channels but another eVar like Internal Campaign ID, Tracking Code etc., because the expiration for both is different and it will never tally with the numbers.
Go through my blog on Last Touch Channel Versus Tracking Code.
Try to breakdown the numbers by Marketing Channel Detail and explore the numbers. Even now, you should see 'Unspecified' in the list because most often we would not have enabled 'Override Last Touch Channel' for Direct and Internal Domains. So, when the users come via Direct after the Paid Marketing Channels, the attribution will still go to Paid Marketing Channels however this time there wont be any Tracking or Internal Campaign code. So, the best metrics to select is if you have any event fired on your 'query string parameter icmp' capture, else, just use the Internal Campaign ID Instances as you shown earlier.
In addition to what everyone else has answered, it is very important for you to remember that Marketing Channels per hit. NOT per visit. That is a very common misunderstanding about Marketing Channels.
Also, remember that AA's definition of visit is primarily time-based, i.e. where there are continuous hits without a break of more than 30 minutes.
So the following is an entirely valid visit in AA, yet notice that the Marketing Channels will change mid-visit:
12:00pm: Arrive at website from campaign, e.g. www.website.com?cid=paidsearch-abc123. --> Marketing Channel = "Paid Search".
12:10pm: Leave website.
12:20pm: Arrive at website from organic search result, e.g. search for "website" at Bing and arrived at www.website.com. --> Marketing Channel = "Organic Search".
12:25pm: Leave website.
2:00pm: Arrive at website from Facebook link, e.g. found a link on the News Feed and arrived at www.website.com. --> Marketing Channel = "Social".
Result of the above:
Paid Search = 1 visit
Organic Search = 1 visit
Social = 1 visit
Total visits = 2 visits -- because Paid Search and Organic Search were within the same visit.