how do we select value of K for calculating NDCG score?

[Eku0194]

Hello,

I am not sure If I fully understand how to select the value of k for getting accurate results. Can you please guide me on which factors should be considered by deciding the k value.

Thank you!

[geraldzakwan]

k is basically the number of top search results you care about, no choice is right or wrong. It really depends on your use case.

In web search (like Google), you might want to use k=10 since generally users are willing to scroll a bit to find the right information.

While in e-commerce (like Amazon), you might want to use smaller k, say k=5, since users don't scroll as much and pay attention mostly to just a few products at the top (I suggest you to learn about positional bias).