The general manager of a popular restaurant noticed that the number of customers in the evening had been decreasing. She promptly ordered the chef to revise the evening menu. Later, customer feedback indicated that the problem was not the menu but poor service from the waitstaff. The manager's decision to have the menu revised suggests that she failed to

Identify and diagnose the problem.

Explanation:

When the manger noticed that the number of customers in the evening had been reducing, the thing that the manager should have done in that case was to identify the problem to know the reason why the number of customers coming has decreased. Identifying and diagnosing the problem will help the manager address the root cause of the problem.

Ordering the chef to revise the evening menu wasn't the right thing to do at that time as that wasn't going to address the cause of the decrease.