In testing controls over invoices, an auditor discovers that in 10% of her statistical sample invoices were sent for full shipments, even if shipping documents suggested partial shipments. In this case, she would likely ________.

a)increase her sample size to determine the extent of the control weakness
b)recalculate control risk to determine if there is any effect on the nature, timing, or extent of her year-end procedures
c)conclude that controls are working at 90% effectiveness and classify control risk as low
d) consult with her partner to consider launching a fraud investigation