Prayer looks directly at securing an answer.  This is its design and it has no other end in view.  There is no greater proof that God does exist then when prayer is answered.  The mere act of praying is no test to our relationship with God.  The act of prayer may be a real dead performance by us.  It may only be a routine habit.  But to pray and receive clear answers, not some of the time but most of the time is the real test of our vital connection with Jesus Christ.  Unanswered prayers are ammunition for infidels and atheist and carries no conviction to the unbeliever.  The answer to prayer is that part of prayer that glorifies God, and brings glory to His name!