How do you measure the effectiveness of your team?

Here are some ways or methods: 

• The quality of work 
  Even though there is no perfect metric to access the effectiveness, you can observe their quality of work if there are different teams involved. 
• The efficiency of work 
  The basic metric is to see whether they could finish their task before a set deadline. You could delegate a task to them and observe the progression of the task from start to finish. 
• Communication between co-workers
  I believe this is one way for workers to express their opinions regarding the workplace or allow them to voice out their suggestions to further improve business processes. It could be as easy as having a sharing session with workers.