Dive deep into card sorting with OptimalSort
Create your card sort
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- How many cards should I use?
- Limiting the number of cards people see in any single card sort
- What should I put on my cards?
- How to create categories for closed or hybrid card sorts
How many cards should I use?
We recommend aiming for between 30 and 60 cards for all card sorts because:
- you’ll get enough useful data to make informed decisions about your content
- you’ll only be able to include the most relevant cards, and be forced (nicely) to discard the rest
- participants will be more likely to complete your card sort.
There are some caveats though…
For an open card sort, 30 to 50 cards will usually account for the complexity of the task and the depth of thought you want from people. You need to balance the need to keep the time commitment to around 10 to 15 minutes with the need to provide sufficient context (enough similar cards) for groups to form.
Closed card sorts with easy grouping options (yes/no/maybe decisions) tend to require less depth of thought and more automatic responses, so going well beyond 60 cards can work really well.
You can create more cards if you’d like to, and set OptimalSort to give a random subset of cards to each participant.
Limiting the number of cards people see in any single card sort
OptimalSort allows you to limit the number of cards from the total set that each person sees when completing a card sort. The temptation is to have lots of cards in your total set and show each person a tiny percentage of the cards. We don’t recommend this because by breaking a sort into a number of smaller sorts, you are in effect conducting many separate sorts. We recommend, if you want to limit the number of cards for participants, ensure that each participant sees 80-90% of the cards. You will also need to increase the number of people who respond.
What should I put on my cards?
The biggest decision to make when creating any card sort is what to put on your cards. Start by opening a spreadsheet or document and collecting all the possible concepts or items you could include in your card sort. Once you have all your ideas on hand, you’ll reduce and refine the possibilities until you’re left with only the most relevant cards.
To come up with your list of possibilities, you could:
- brainstorm and mind map all the different information you want to include on your website
- get your hands on documentation, like a sitemap, org chart, or product inventory
- complete a content audit of your website or knowledge base and only select the most relevant items or article titles
- get a list from stakeholders telling you exactly what they want to see
- study your intended customers to find out the kinds of information they’d find useful
- research what similar organizations (or even competitors) have on their websites.
Create a concept or item that can be grouped
Card sorting tests concepts, not usability – your goal is to discover how people think about and make sense of your information, not whether or not they can find it quickly on a homepage.
The cards themselves don’t need to be written in the most ‘usable’ format, or exactly as they are on your website. Jakob Nielsen points out that “It’s OK to actually reduce the usability of the cards, because people don’t actually use them in the UI [user interface]”.
The cards need to be on the same conceptual level and similar enough for participants to actually be able to sort them into groups. By conceptual level, we mean that if you want people to sort grocery items, you won’t include the higher level category ‘Vegetables’ as a card at the same time as the lower-level ‘Carrots’:
In her book on card sorting, Donna Spencer is firm on the importance of making sure all cards are actually groupable. She cites the example of a 100-card card sort she tested with a colleague before taking it to a client. Her colleague was unable to create coherent groups because the cards were inconsistent and often unrelated, and therefore the card sort couldn’t “provide much insight into how the content could be grouped on the site”.
The solution? She recommends reviewing your card sort with this in mind to make sure “each item…could have a potential partner (or many partners)”. Ask someone to test it out for you (which you can do by sharing a study preview link with people in your team).
And if you find a card that is difficult to partner with any others, but that you think is valuable to your study, follow Donna’s lead: “On a recent sort, I deliberately included three cards I didn’t really need… so participants would have some cards that were easy to group… [to give] participants the confidence to proceed to more difficult groupings.”
Avoid patterns in words, casing and structures
When you ask people to complete a card sort, you’re asking them to look for and create patterns with your cards. The human mind is so fond of pattern-finding that we use it regularly as a shortcut when making decisions, especially on intellectually-taxing tasks.
For user research, this is one of the great strengths of card sorting, and one of its biggest pitfalls. If you include enough cards with the same opening phrases, casings, and sentence structures, it’s likely that most people will group them together — but instead of them approaching it conceptually, they’ve quickly, and without realizing it, played a simple game of Snap.
Jakob Nielsen illustrates the issue with these example cards, that are written the way they would be on a website, but that offer too-obvious pairings:
To solve this, Nielsen recommends editing your labels using synonyms and non-parallel structures, an approach that doesn’t need to involve extensive rewrites. Instead of ‘Harvesting strawberries’, we could say ‘Picking strawberries’; and instead of two cards that begin with planting, you could make their structures different by labeling one ‘Planting corn’ and another ‘Wheat planting’.
Including images on your cards
Images can be as effective as text for representing concepts and items, and in some cases more so. You can include images to illustrate or clarify the text on your cards, or you can include images on their own.
You might choose to add images to your cards if you:
- have products your customers will expect to see as images, like clothes, appliances, and furniture
- design portfolio or photography websites and want ideas for grouping images
- want to find out what people think of your sketches or designs.
In OptimalSort, you can upload JPEG or PNG files of any size, and each image will be resized to a maximum width of 200px. Resize all your images before you upload them if you want them to be the same size, and preview your card sort to make sure it looks how you want it to. Giving each image a descriptive label will make your analysis easier.
How to create categories for closed or hybrid card sorts
When you’re creating a closed or hybrid card sort, take care to craft categories that help you achieve your objectives.
For closed card sorts, you need to create enough categories that people can find a home for your cards. Try not to add too many categories that match your intentions for your website or research questions. The more categories you create, the more options participants will have, and the more likely it’ll be that you find out which categories are preferred over others.
When you run closed and hybrid card sorts, the categories you set will lead people to think about your cards in a particular way, whether it’s on purpose or not.
For example, if you run an open card sort with 40 cards containing grocery items, you might find that some people group the items by type (vegetables, fruit, dairy) and some by meal (breakfast, lunch, dinner). If you run a hybrid card sort with even just one category, most people will take your lead: Set the category ‘Vegetables’ and most people will create the category ‘Fruit’.
The number and type of categories you set for a hybrid card sort will determine whether the card sort is more open or more closed:
- When you set fewer categories, participants are more likely to create their own, and thus it will tend towards open.
- When you set more categories, enough for people to find a home for every card, they’re less likely to create their own categories, and thus it will tend towards closed.