Defining god, and defining prayer are first needed to establish the efficacy of praying.

The definition in the OP that prayer consists of ‘asking for something’ from a separate entity..i.e.god. Is a common definition yet i feel deeper probing into many religious texts allude to a more subtle nature and function of prayer. Just like the notion of god, alludes to a more complex ‘being’ than just a separate entity sitting on a throne, blessing some, smiting others.

The statistics for ‘answered prayers’ probably point to it being a gamble and really serves to help a person feel better, than the prayer actually being ‘answered’.

Whereas there are more subtler forms of prayer occurring constantly by us all that are being answered.