When your search is first displayed, it is surrounded by related terms, so there is much less chance of a false drop as with the East of Eden example.
Also, keyword searches in these tools are prone to false drops.
A false drop
can occur if the webpage found contains the keywords entered in the search, if the webpage is an attempt at spamdexing, if the search engine used has a fault in its database, or if it has a bug in the query program.
The next step in the query processing is the false drop resolution.
Here, the signature length should be increased to maintain the false drop probability at minimum.
Although this approach gives some space saving, the number of false drops will definitely be increased due to sparse signature files.
When we can work out to our satisfaction how the false drop
occurred (perhaps a misspelled word), then we feel we can trust the search engine.
The equations used to calculate the signature weight and width are obtained so that the false drop probability is minimized and are proved in Roberts  and Davis and Kamamohanarao .
It was previously proven that the storage requirement for the single-level signature file (SLSF), the 2LSF, and the MLSF indexing methods is the same if they all have the same global false drop probability [Lee et al.
Better retrieval can be achieved because of the semantic values attached to the terms; this would help reduce the false drops
In xrefer you may also find false drops
that are unavoidable, especially in single-word searches, such as those results that list people whose first, middle, or last name is Hercules, not to mention the C-130 Hercules military airplane.