How To - Create an Index

Hi, I'm new to this. I've always wished to create an index, for hobby and all.

Not the kind of index at the end of lengthy books, but the statistical kind, like a happiness index - happiness index - Google Search

Here are two examples of types of indexes (there are thousands more):

Human Development Index - Wikipedia, the free encyclopedia
Quality-of-Life Index - Wikipedia, the free encyclopedia

In the past, I've read basic statistics-related stuff, but they have never gotten me anywhere near helpful.

So in any event,
How do I go about this?

Please in plain English. Links are always helpful. Thank you.