6 , ▁R ho ades ▁published ▁an ▁article ▁looking ▁at ▁whether ▁the ▁Aud itory ▁Ver bal ▁approach ▁was ▁just ified . ▁Using ▁Fr att ali ’ s ▁system ▁for ▁we igh ing ▁the ▁strength ▁of ▁treatment ▁evidence ▁based ▁on ▁the ▁degree ▁of ▁scientific ▁rig our , ▁she ▁found ▁ 7 ▁studies ▁concerning ▁the ▁AV ▁approach ▁of ▁class ▁II ▁level ▁evidence . ▁She ▁concluded ▁that ▁even ▁with ▁the ▁minimal ▁number ▁of ▁studies , ▁there ▁was ▁evidence ▁" for ▁the ▁valid ity ▁and ▁effect iveness ▁of ▁the ▁A - V ▁inter vention ▁model ". ▁Following ▁on ▁from ▁R ho ades ’ ▁work , ▁Hog an ▁et ▁al . ▁( 2 0 0 8 ; ▁ 2 0 1 0 ) ▁published ▁out comes ▁for ▁children ▁in ▁an ▁AV ▁programme ▁which ▁were ▁essentially ▁quasi - ex perimental ▁studies ▁in ▁that ▁the ▁assess ment ▁tool ▁used ▁had ▁been ▁standard ised ▁on ▁typically ▁developing ▁children ▁and ▁so ▁a ▁comparison ▁could ▁be ▁drawn ▁between ▁the ▁age ▁equivalence ▁scores ▁obtained ▁by ▁the ▁children ▁on ▁the ▁study ▁and ▁their ▁chron ological ▁or ▁‘ he aring ’ ▁age . ▁( The ▁hearing ▁age ▁of ▁a ▁child ▁is ▁the ▁duration ▁of ▁time ▁since ▁the ▁child ▁has ▁had ▁optimal ▁access ▁to ▁sound .) ▁In ▁these ▁studies , ▁the ▁average ▁rate ▁of ▁language ▁development ▁increased ▁significantly ▁during ▁the ▁time ▁on ▁the ▁programme ▁compared ▁to ▁the ▁average ▁rate ▁of ▁language ▁development ▁prior ▁to ▁emb ark ing ▁on ▁the ▁programme . ▁D orn an ▁et ▁al . ▁( 2 0 0 9 ) ▁review ed ▁the ▁evidence