Recommender System Flashcards
What is “Top-N recommenders”? Give 3 Examples
Produce a finite list of the best things to present to a given person.
What is Explicit feedback? Give 3 Examples
Directly ask for users’ interest.
Example: Rating, Reviews, Like/Dislike
What is the disadvantage of Explicit Feedback?
Humans can get tired of providing so much feedback, and will not reliably provide accurate or truthful feedback
What is the advantage of Explicit Feedback?
Clear preferences: Explicit feedback provides clear indications of user preferences and opinions. Interpretable: Ratings and reviews are straightforward to interpret and incorporate into recommendation models
What is Implicit feedback? Give 3 Examples
Look at users’ behaviours and interpret them as indications of interest or disinterest.
Example: Purchase History, Click-Through Rate (CTR), Viewing Time
What is the disadvantage of Implicit Feedback?
Lack of explcit preferences: Implicit feedback might not precisely reflect users’ true preferences, leading to potential ambiguity.
Difficulty in interpreting: Understanding the exact meaning of implicit signals can be challenging.
What is the advantage of Implicit Feedback?
Abundant data: Implicit feedback is often more abundant than explicit feedback, as it is generated passively during user interactions.
Less user effort: Users don’t need to explicitly rate items, making implicit feedback collection less intrusive.
List some accuracy metrics to evaluate a recommender system.
Examples: Mean Absolute Error, Root Mean Square Error.
Why do accuracy metrics matter?
It provides an offline and immediate evaluation methods for tuning, comparing and benchmarking the model.
However, accuracy and rating predictions have limited value in practice, as the goal is not to minimize the error, but to find what people like. Fundamentally, it’s impossible to evaluate the value of a recommender system offline.
What is Hit Rate?
the proportion of users for whom the system made at least one relevant recommendation.
Why does Hit Rate Matters?
A higher Hit Rate indicates that a larger portion of users received recommendations they found useful, contributing to overall user satisfaction.
What are considerations of using Hit Rate?
The larger the list of recommending items, the higher the hit rate is. Therefore, choose a reasonable value for L
What is Average reciprocal hit rate (ARHR)?
a hit but it accounts for where in the top end list the hit appear.
Why does Average reciprocal hit rate (ARHR) matter?
A higher ARHR score implies that the system is effective in identifying and placing relevant items at the forefront of the recommendation list.
What is Cumulative hit rate (cHR)?
Add a threshold for the test set so that we test on items with acceptable ratings.
Why does Cumulative hit rate (cHR) matter?
We shouldn’t get credit for recommending items to a user that we think they won’t actually enjoy
What is Coverage?
the % of (user, item) pairs that can be predicted or percentage of possible recommendation that the recommender system can provide.
Why does Coverage matter?
The ability of the recommender system to recommend all items from a train set to users.
What are considerations of using Coverage?
There can be a trade-off between coverage and accuracy. A system with the ability to recommend all items to a user is no different than a random prediction.
What is Diversity?
How broad a variety of the recommending items. (1-S), in which S is the average similarity between recommendation pairs.
Why does Diversity matter?
Avoid repetitiveness and discover user’s new interests
What are considerations of using Diversity?
High diversity is not always good. You can achieve very high Diversity by just recommending completely random items.
What is Novelty?
A measure of how popular the recommending items.
Why does Novelty matter?
Novelty can help to increase user engagement and satisfaction