Sequencing tests can look very simple, but there are a number of complexities to think about - and mathematically, the numbers get very large very quickly.
As an example, here's the Ford UK's cars category page, www.ford.co.uk/cars.
[The page scrolls down; I've split it into two halves and shown them side-by-side].
Testing sequences can quickly become a very mathematical process: if you have just three items in a list, then the number of recipes is six; if you have four items, then there are 24 different sequences (see combinations without repetition). Clearly, some of these will make no sense (either logically or financially) so you can cut out some of the options, but that's still going to leave you with a large number of potential sequences. In Ford's example here, with 20 items in the list, there are 2,432,902,008,176,640,000 different options.
Looking at Ford, there appears to be some form of sorting (default) which is generally price low-to-high and slightly by size or price, with a few miscellaneous tagged onto the end (the Ford GT, for example). At first glance, there's very little difference between many of the cars - they look very, very similar (there's no sense of scale or of the specific features of each model).
Since there are two quintillion various ways of sequencing this list, we need to look at some 'normal' approaches, and are, of course, a number of typical ways of sorting products that customers are likely to gravitate towards - sorting by alphabetical order; sorting by price or perceived value (i.e. start with the the lower quality products and move to luxury quality), and you could also add to that sorting by most popular (drives the most clicks or sales). Naturally, if your products have another obvious sorting option (such as size, width, length or whatever) then this could also be worth testing.
What are the answers? As always: plan your test concept in advance. Are you going to use 'standard' sorting options, such as size or price, or are you going to do something based on other metrics (such as click-through-rate, revenue or page popularity)? What are the KPIs you're going to measure? Are you going for clicks, or revenue? This may lead to non-standard sequences, where there's no apparent logic to the list you produce. However, once you've decided, the number of sequences falls from trillions to a handful, and you can start to choose the main sequences you're going to test.
For Ford, price low to high (or size large to small), popularity (sales), grouping by model size (hatchback, saloon, off-road/SUV, sports) may also work - and that leads on to sub-categorization and taxonomy, which I'll probably cover in an upcoming blog.
