Precision % relevant in results

1
WJ Chapter 12 - Evaluating Results

• Precision relevant in results docs relevant
  in results
• 1 100 relevant docs in results
• Recall
• relevant retrieval docs relevant in results
• 1 100 recall docs relevant in database
• Just a CONCEPT! To use as a rough rule of thumb
  (guide) cant really measure
• High Precision Search just want a few good
  docs, low junk
• (use AND, use fewer terms, use DEs, limit to Ti,
  Ab, use other limits)High Recall Search want
  comprehensive, dont miss much!
• (use lots of synonyms, free text (and
  controlled), very few limits)
• Note NICE TABLE pg 266
• ???? ???? ???? ???? ????
• When Are You Done?
• With practice you get better at determining when
  you have done enough. It depends on what your
  requestor wants and on when you get to the point
  of fewer and fewer relevant results being pulled
  out. ? ? ? ?
• Always Grow!
• What worked well
• What didnt work

Overriding question WHAT IS RELEVANCE? Ans it
depends Its up to user and may not be the
obvious best fit result
2

• Precision
• relevant in results docs relevant in results
• 1 100 relevant docs in results
• Recall
• relevant retrieval docs relevant in results
• 1 100 recall docs relevant in database
• QUESTION 1
• DB 100 docs total and 80 are relevant,
  retrieve 25 docs, 20 of these are relevant.
• Precision ________ Recall ____________
• 20/25 .8 (80) 20/80 .25 (25)
• QUESTION 2
• 2
• QUESTION 3
• 3