The Trouble with the new Threshold Goals in Google Analytics (or be careful
with your interpretation of data)
This article is based on the new Google Analytics (GA) threshold goals, and some warnings on analysis problems you
are likely to encounter when analysing your web content.
These limitations are not terrible, but can cause confusion when analysing the data especially when using the new
threshold (time on site and pages / visit) goals.
How did goals used to work?
In prior releases of GA users were limited to 4 goals per profile, this meant if your website had more than 4
conversion goals (eg watch video, download brochure, comment on article, sign up for newsletter, view 'about us'
page) you were required to either create an additional profile to capture goals or to use eCommerce tracking to set
up goals as products. Some users weren't happy with this limitation.
What's changed?
Google have extended the goal functionality to enable up to 20 goals per profile now, in order to organise the goals
for reporting purposes the 20 goals are organised into what are known as "goal sets", which are essentially buckets or
folders each containing 5 goals.
What's also happened is that new types of goals have been introduced with what are now known as "threshold
goals". Threshold goals on first glance appear to be very useful - we can now track goal conversion (eg) for visitors
who spend, say, more than 3 minutes on the site or view more than 4 pages / visit. The idea behind this is that
perhaps your site is about content - like a YouTube for example - then one of your goals is to get visitors to view
more content and to spend longer on the site. Not bad, right? So, the threshold goals allow you to set conversion
thresholds - multiple times - so (eg) you can 'convert' a visitor who spends 1mins on the site, 2mins, 5mins, 10mins
etc.
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In the example above you can see how I've created two sets of goals, one for more traditional content conversion
(view form, submit form, view certain pages); the other set is based on time on site thresholds that I've set for 1, 2,
3, 5 & 10mins on site.
What's the problem?
The ability to create these threshold goals is quite nice, but can cause quite large problems with standard reporting if
you aren't careful with which metrics you are analysing. Take a look at the examples below, I'm using a secondary
dimension report (Network Location, City) to help me understand who's coming to the site:
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The problem is with the ‘conversion rate’ metric. From a logical perspective this value is correct, what GA
is going is aggregating the multiple goals together into a sum value, from an analysis perspective this can
cause problems. If you look at the first screenshot for Goal Set 1, you’ll notice (sadly) that none of the
goals have shown any conversions – yet our goal conversion rate is 59%, this is because our engagement /
threshold metrics for the 1 min on site and 2 min on site are converting very well. This isn’t necessarily
providing me with a true measure – especially when the cascading time on site values aren’t de-duplicating
as a visitor spends longer on the site. Let’s look at a very simple example:
1 Visitor comes to the site and spends 12 minutes and leaves. For this visitor we’re going to see each of
the 5 threshold goals show 100% conversion, in other words this visitor has converted at 500%. We can
argue about the inability of averages to work either, by adding another 4 visitors who see 2 pages and
leave after less than a minute: now our conversion rate is 100%. That’s another issue though!
What does this tell us? Not a great deal, however at an individual goal level this is useful data.
In summary:
Make sure you look at the metrics that GA offers very carefully so you don’t end up drawing incorrect
assumptions from your data – and if you’re using multiple threshold metrics try to avoid looking at the
‘goal conversion rate’ metric as it can be somewhat misleading, with this in mind I would recommending
using only one of each of the two kinds of threshold metrics.
In order to set your thresholds perhaps you already have
a model that tells you x mins on site or y pages / visit is
profitable – in which case use your KPI’s, otherwise take
a look at your averages for these metrics and add (eg) 1
standard deviation above the average to help you
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identify the top ~15% of visitors. Through application of the central limit theorum you can adjust your
threshold metrics to select different populations.
Now, wouldn’t it be nice if GA intelligence helped you out with these calculations!
It’s worth remembering that you can apply these same threshold metrics in advanced segments as an
alternative way of determining your threshold limits.
Something also worth considering at the moment, is that
the 20 goals are not currently available in custom
reporting, this is likely to be a release for future – but the
new goals as implemented won’t be available for (eg)
creating revised traffic source reports with custom
threshold goals (excluding the overall goal conversion
rate).
The new goals also aren’t available yet in advanced
segments which is also worth considering for future
analyses.
What should Google do?
I would recommend two courses of action:
1. Remove the overall goal conversion rate metric, or
2. Replace the overall goal conversion rate metric with a new ‘goal set conversion rate’ to make the
metric column appropriate to the tab of the report.
Enjoy making use of these new features, but please be careful with your analysis!
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