The factors that affect the accuracy are as follows:
The main factors that affect the precision rate are: index words can't accurately describe the theme and retrieval requirements of literature; The assembly rules are not strict; The choice of words and the relationship between words are incorrect; Gonta is fine; Assembly error; The specificity of search words (or search expressions) used in retrieval is not enough, and the retrieval range is wider than the retrieval requirements; The retrieval system does not have logical negation function and feedback function; The number of words allowed in the search formula is limited; Improper truncation position, improper use of logical "or" in retrieval formula, etc.
In fact, the factors that affect the retrieval effect are very complicated. According to experiments made by foreign experts, the recall rate is inversely proportional to the accuracy rate. To search completely, it is necessary to gradually relax the scope and restrictions of retrieval, and as a result, many irrelevant documents will be brought in, which will affect the precision rate.
It is not easy to try to improve recall and precision at the same time. On the one hand, it is inappropriate to emphasize and on the other hand, it is inappropriate to ignore. The recall and precision should be adjusted reasonably according to the requirements of specific topics to ensure the retrieval effect.
Precision is an index to measure the signal-to-noise ratio of retrieval system, that is, the percentage of relevant documents detected and all documents detected. Generally expressed as: precision ratio = (the amount of relevant information retrieved/the total amount of information retrieved) x 100%.
Limitation of precision ratio
The limitation of precision is as follows: if the retrieval results are in the form of titles instead of full text, it is difficult for users to judge whether the retrieved information is closely related to the theme because of the simple title content, and they must find the full text of the title to correctly judge whether the information meets the requirements of the retrieval theme; At the same time, the relevant information mentioned in the accuracy rate also has the limitations of "hypothesis".
Experiments show that there is an opposite interdependence between recall and precision: if the recall of the output is improved, its precision will decrease; or vice versa, Dallas to the auditorium