When controls "work" the auditor increases the amount of substantive testing the auditor reduces the amount of substantive testing the auditor increases the amount of substantive testing over what would have been done if the control had been effective in preventing or detecting misstatements in the financial statements the auditor decreases the amount of substantive testing over what would have been done if the control had been effective in preventing or detecting misstatements in the financial statements the auditor reduces the amount of substantive testing over what would have been done if the control had not been effective in preventing or detecting misstatements in the financial statements