How do you determine when needs analysis should be conducted-Is it always necessary to conduct a TNA?

Bus 680 needs analysis

Describe in detail how you would respond to and proceed in this situation. In your post, respond to the following questions:

What is the purpose of a training needs analysis (TNA)?
How do you determine when needs analysis should be conducted?
Is it always necessary to conduct a TNA?
What methods and tools would you use to help this manager?