<prompt> While analysis of data, allocation into similar groups is done to ensure-ComparabilityAccuracyValiditySensitivity  <response>: In a case-control study, the controls may differ from cases in a number of factors like age, sex, occupation. - it is necessary to ensure comparability between cases and controls. - this process is called matching. Reference: Parks textbook of preventive and social medicine, 23rd edition, pg no:72 