Offer new experiences as recommendations, or risk blinding visitors. Since accurate and relevant product recommendations have become standard practise, website visitors have started to ignore these parts of the website. Adding novel products and new information into the mix will be the answer to the issue of recommendation blindness. Accuracy and relevancy are still relevant, but now recommendations also require novelty and serendipity to convert. Novelty means that the products should be new to the user and serendipity means that they should be attractive and surprising as well. Offer something beyond the obvious to create positive, surprising experiences. Open people’s eyes, don’t blind them. Vesa-Matti Hyppönen is a Team Lead Developer at FROSMO, working in the customer service function. You'll find the video of this, and other inspiring FrosmoX16 presentations, on www.frosmo.com/frosmox16

1. Beyond relevancy and accuracy
in recommendations
FrosmoX16
Vesa-Matti Hyppönen 24.10.2016

2. This is Mekbib
2
● This is Mekbib and his 2 year old son
● He is sitting outside in a cafe
● His shirt is blue
● Mekbib could not make it here today
This is all accurate, but not very relevant in
current context

3. This is Mekbib
3
● This is Mekbib and his 2 year old son
● He works at Frosmo in the customer
service function
● I am his replacement as a speaker today
● Mekbib could not be here because he
couldn’t not fit his hair into a passport
picture
Accuracy without context and relevance
could be misinformation

4. You also need Relevancy
4
• Google search for “The lion king” = 13 600 000 results
• All these documents have many occurrences of the word “The”
• Less frequent occurrences of “Lion” & “king”
• Teaching the recommendation machine to find relevant data
• To offset the abundance of “The”, we lower the weight by checking its term
frequency and inverse document frequency

5. Tf-idf used to determine Relevancy
5
Tf-idf is a weighting factor to show how important an item is related to the whole corpus

6. Why is Accuracy + Relevancy != Enough?
6
• Recommendations can produce accurate and relevant info but be useless
• Because it fails the test of obviousness
• Because it fails to give the users any new info
• Wasting valuable screen estate, resources and money
• Factor in previous user interaction on site

7. We need to add the element of novelty & serendipity
7
• Novelty = Recommending undiscovered items
• Serendipity = Measure of how the items are attractive and surprising to the
user
• Unexpectedness and usefulness
• Judged from subjective perspective

8. How to measure serendipity?
Collaborative filtering
- Memory based, easier, neighbourhood based
- Model based, more complex - non obvious
Neighborhood based automatic
collaborative filtering using pearson correlation
8

9. Conclusion
9
• Obvious recommendations
• Waste space by fail to introduce new items or giving users information
they already know
• Make user blind to website real estate
• Recommendations should rise beyond accuracy and relevancy
• They should be novel and serendipitous as well
• Technically challenging but will self adust user classification
• Don’t forget to A/B test - results might be surprising

10. Thank You
www.frosmo.com
Vesa-Matti Hyppönen
Developer
vesa-matti.hypponen@frosmo.com
+358 50 3625734