Quantifying End user experience

Hi ,

We are optimizing sql queries and want to quantity end-user/business user's experience improvement after improving query execution. But we find a query is taking 6 seconds to execute from awr report, but the screen which is triggering the query is loading in 2 seconds. My questions are:-

i) How can this be possible?

ii) How can we quantify end-user response time improvement due to sql optiization?

iii) What things I need to check to explain this scenario?

Thanks