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This usually comes down to 2 questions:

• How many trees are you we testing at a time?
  
  
• Are you we testing the whole tree, or just part of it?
  
  
  

If you’re we’re testing an existing tree for problems, before starting your our IA redesign, the answer here is simple – you’re we’re testing just the one tree.

If you’re we’re revising the IA for a site, and you we haven’t done a baseline test yet, it’s a good idea to test the “before” and “after” versions. At minimum, this means testing two trees – the existing one (to get a baseline score) and your our revised tree (to see what improved and what didn’t).

As mentioned above, though, you we really should be testing more than one alternative, so you we can be sure your our eventual new tree is as effective as possible. Typically, we’ll test 2-3 proposed trees against each other (and against the existing baseline tree), then we’ll test a “best of” hybrid of the two in a second round.

For more on testing alternative trees against each other, see The design phase: creating new trees in Chapter 3.

If you’re we’re testing a small or medium-sized tree (say, < less than 500 items), you we will normally test the whole tree – no major pruning required.

If your our tree is larger (say, 500-1000) items, you we have 2 options:

• Test the whole tree – Easy to prepare, but affects how many tasks you we can ask each participant.
  
  
• Test a “pruned” version of the tree – Takes some effort on your our part, but lets you us concentrate on the parts you’re we’re really interested in.
  
  

Finally, if your our tree is very large (>1000 more than 1000 items), testing the whole tree may be feasible, but in most cases we recommend that you prune your pruning the tree to keep the participants’ effort from becoming onerous.

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