Measuring Search Relevance by Hugh E. Williams.
From the post:
The process of asking many judges to assess search performance is known as relevance judgment: collecting human judgments on the relevance of search results. The basic task goes like this: you present a judge with a search result, and a search engine query, and you ask the judge to assess how relevant the item is to the query on (say) a four-point scale.
Suppose the query you want to assess is ipod nano 16Gb. Imagine that one of the results is a link to Apple’s page that describes the latest Apple iPod nano 16Gb. A judge might decide that this is a “great result” (which might be, say, our top rating on the four-point scale). They’d then click on a radio button to record their vote and move on to the next task. If the result we showed them was a story about a giraffe, the judge might decide this result is “irrelevant” (say the lowest rating on the four point scale). If it were information about an iPhone, it might be “partially relevant” (say the second-to-lowest), and if it were a review of the latest iPod nano, the judge might say “relevant” (it’s not perfect, but it sure is useful information about an Apple iPod).
The human judgment process itself is subjective, and different people will make different choices. You could argue that a review of the latest iPod nano is a “great result” — maybe you think it’s even better than Apple’s page on the topic. You could also argue that the definitive Apple page isn’t terribly useful in making a buying decision, and you might only rate it as relevant. A judge who knows everything about Apple’s products might make a different decision to someone who’s never owned an digital music player. You get the idea. In practice, judging decisions depend on training, experience, context, knowledge, and quality — it’s an art at best.
There are a few different ways to address subjectivity and get meaningful results. First, you can ask multiple judges to assess the same results to get an average score. Second, you can judge thousands of queries, so that you can compute metrics and be confident statistically that the numbers you see represent true differences in performance between algorithms. Last, you can train your judges carefully, and give them information about what you think relevance means.
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An illustrated walk through measuring search relevance. Useful for a basic understanding of the measurement process and its parameters.
Bookmark this post so When you tell your judges what “…relevance means”, you can return here and post what you told your judges.
I ask because I deeply suspect that our ideas of “relevance” vary widely from subject to subject.
Thanks!