CSCE 470 Lecture 4

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Empirical Investigation of effect of ranking

Videotaping

Interviewing Thinking aloud Eye tracking

Rank is important: there are a few "click monkeys"

Calculating Rank

• If (keyword on Wikipedia), get bonus points
• Number of keyword counts (in title? in URL?)
• Popularity (clicks, dwell time, tweet mentions, Facebook likes)
• PageRank structure
• Aesthetics
• Load Time
• hosting malware or email harvesting crap.
• Machine learning rankers

Vector Space Retrieval

One of the (four) most important things in the course.

(No really, he will call you randomly 5 years later and ask.)

also known as:

• Bag of Words Model
• Vector Space Model

$n$-dimensional space

Each document is a vector in this space.

Queries exist in same space, and ranking is just distance between document and query.

$q$	D1	D2
Johnny Football	Johnny played football today	Johnny is a bad example

• Which document is closer to the query
• What is the information need? (news, autographed merchandise, purchase something, etc.)