Card Sorting

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This is a simple technique that enables one person or a group of people to create a categorisation of objects so that it is understood which objects belong with which other objects. Objects can be anything: menu items, blocks of content, proposed web pages, URLs. This method can be used by practically anybody after a few minutes practice.

How to do a simple card sort

First of all, on a set of index cards, write down names for all the objects you wish to sort. This is sometimes best done in a small group, as a brainstorming exercise, but if you are re-doing an application that already exists, it is sufficient at first to simply write down the names of the objects from the application. One object per card. Number the cards on their reverse side for identification.

On a table in front of you, put cards in piles depending on their similarity or degree of fit with each other. At first you may have many different piles of cards, nothing may seem to go with anything else, but after a while you will generally find that you begin to see points of contact. You may, if you wish, include positive and negative instances in the same pile. This is entirely up to you.

That's it! Your first card sort. Note down the numbers of the cards in each pile. This is the record of your card sort.

More complex variations

There are a number of variations you may wish to play on this theme:

  1. You may get others to do the card sorts for you, rather than doing it yourself. A good idea, if you are trying to sort content into categories is to get some representative end users and ask them to sort the content cards for you.
  2. You may decide for various reasons to restrict the number of categories or piles of cards that will be created. This is called a Procrustean procedure for card sorting. You may even dictate the names of the piles, for instance, if you are assigning drop-down menu items to a menu bar.
  3. You may ask not only that the cards be sorted into piles, but that the piles themselves be arranged in some kind of order as well. The best technique here is to use the two dimensionality of the table, and to ask the user to move the completed piles around so that piles which are similar are put close together, and piles which are far apart are kept apart. You will most probably find yourself doing this automatically at the start anyway, and so will your users.

Instead of sorting cards, you may wish to do the whole operation on a computer. The simplest technique is to use a spreadsheet as follows, but you will also find various computer programs have been designed specially to assist this kind of task.

  1. Write the name of each object in a separate cell, all the way down one column of your spreadsheet. You are advised to make this column the second column.
  2. Now go through the objects, and assign a number to each object, putting the number in the cell to the left of the one bearing the description. Use the numbers 10, 20, 30 and so on to start with, and assign the same number to objects which would go into the same pile if you were card sorting.
  3. When you have assigned a number to each object, you can then use the spreadsheet 'sort' function to arrange the objects in order, and to ensure that all similarly-numbered objects are together.
  4. Depending on how you feel about your first sort, you may change numbers, add extra number categories, or insert second-order categories by using units, so for instance items in the 20 range may be sorted into 20s, 22s, and 26s.

Combining Brainstorming and Card Sorting

Card sorting may be used in a group situation as part of a more elaborate knowledge elicitation procedure. A suggestion for such a procedure, which has been used quite successfully on a number of occasions, is as follows.

  1. Assemble a group of users, and start like a focus group in order to get everyone thinking about the same set of issues.
  2. Switch into 'brainstorming' but require that each delegate writes down each of their ideas on a stick-it or some other kind of paper slip that can be temporarily affixed to a wall.
  3. Now request that each delegate go to a communal wall space and stick their stick-its on the wall. Advise them to put similar stick-its close together. New stick-its may be generated at any time.
  4. Let the group carry on with this until they are satisfied that they have grouped and sorted all the stickits they have generated.
  5. Request someone from the group who has shown themselves to be a leader personality type to summarise for you, in front of the group, the rationale behind the grouping.
  6. Ask if there are any dissenting opinions, and why.

It has been reported that such a 'concept wall' may be generated in a communal area or one in which there is a flow of people during the normal working day, and that over the space of several days to a working week, anybody with access to this space is free to re-arrange, and add stick-its. It is generally a good idea to forbid the destruction of stick-its, but a 'trash can' area may be designated on the wall space for discarded stick-its.

Conclusion: advantages and drawbacks

Card sorting and its variations are very simple and effective methods for eliciting the structure of objects. They have been widely used in numerous guises. There are no known drawbacks to these methods and there is much to be gained from their adoption.

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Copyright EMMUS 1999.
Last updated: September 29, 1999.