Some generalizations about recall and precision must be said before evaluating the recall and precision of different search engines. Secondly, people tend to assume that a high precision means a good search. In fact this may indicate low recall as the person searched in a very small data base and consequently missed mu ch relevant information on the particular subject of research. And finally, it's hard to determine recall, since we don't know how many relevant items are in the data base. With that said, let's compare the recall and precision of the search engines based on our search for usage-based billing software.
Precision is the proportion of the items found that are relevant to the search.
Recall is the proportion of all the rele vant items in the database found in the search. I assumed that there are only 15 relevant sites in the world wide web. Therefore we can see that Yahoo, WebCrawler, and HotBot performed better than Altavista according to the measurement methods of recall and precision. However size is definately not the only factor, since Google performed well and it has a data base larger than Altavista's data base. The main problem facing large data bases are the relevance of the documents retrieved.