Inside a Recommendation Machine: teacher key

How Video Sites Pick Your Videos, grade 8 edition, written for 8th grade. Video apps use stages to cut billions of videos down to your feed. Read how the stages work, why they are built to keep you watching, and how to stop.

Read the book. Print this page for the key.

Questions and answers

1. What is the first stage of recommendation described in Google's course notes?
   • Candidate generation (answer)
   • Re-ranking
   • Scoring
2. What can re-ranking do?
   • Delete the user's account
   • Remove items the user disliked or boost fresher content (answer)
   • Make every video longer
3. YouTube said it added watch time to its recommendations in which year?
   • 2011
   • 2021
   • 2012 (answer)
4. Why does Common Sense Media say YouTube's business model rewards watch time?
   • Ads are not used
   • The longer users watch, the more YouTube makes in ad sales (answer)
   • Longer videos cost more to make
5. What does the word candidates mean for a recommendation system?
   • Possible videos to pick from (answer)
   • People who vote
   • Sounds in a video

Words

• candidates: possible picks
• algorithm: selection program
• diversity: a mix
• engaged: kept watching