Hey there, associate analyst is basically the most jonior level position. Typically the structure goes like this:
Associate analyst->analyst->associate-VP/AD etc.
For some of the banks they dont necessarily have the associate analyst position and therefore it will start from the analyst level directly
As to whether or not you are competent enough for the work I would say they recruit you for a reason. If they give you an offer that means they trust that with some sorts of training you should be qualified for your work.