Problem in Identifying relevant documents to evaluate Precision in Information Retrieval (IR) Systems In searching engines, especially for ranked search approaches, How to evaluate the results returned by IR Systems . The precision is evaluated by the below equation:

(Number of relevant documents in retrieved documents)/(Number of retrieved documents).

However, how to decide which returned documents are relevant for the given query? For that, should we go through each returned document to find if it is relevant or not?  Or should we say if any returned document contains all the query keywords?
Yes, the client needs to figure out which of the results are actually relevant. For obfuscation reasons the server returns irrelevant documents and also cannot know which documents are irrelevant so the client has to make that distinction.