<prompt> IQ for sever mental retardation -2020-3535-5050-70  <response>: WHO classification of Mental retardationMR mild MR...IQ 50-70 moderate MR ...35-49 severe MR..IQ 20-34 profound MR...IQ under 20 ref; page no;582 23rd edition of PARK;s textbook of Preventive and Social medicine 