Test of controls provide evidence for issuing an opinion on internal controls and the reliability of information systems. When testing financial statement assertions, an auditor can assess reasonableness through analytical procedures, directly test account balances, or use a combination of control and account balance testing. Sampling involves applying procedures to less than 100% of transactions and increases likelihood of a representative sample by using a sufficient size selected from the proper population. Test of controls is done to express an opinion on internal controls, assess control risk, ensure compliance, or test account balances. Risks include nonsampling errors and sampling risk of an incorrect inference from a small sample. Sample size depends on the misstatement size that would impact the assessment and desired confidence level when making inferences.