Current Slide

Frequent terms are less informative than rare terms

Consider a query term that is frequent in the collection (e.g., high, increase, line)

A document containing such a term is more likely to be relevant than a document that doesn’t

But it’s not a sure indicator of relevance.

→ For frequent terms, we want high positive weights for words like high, increase, and line

But lower weights than for rare terms.

We will use document frequency (df) to capture this.