I have a query that displays different execution plans on my production and development servers. If I look at the "estimated execution plan" through QA the same SQL statement is doing a multiprocessor access in development and single threaded processing in production.

Also the statement in production is spending 17% on a hash statement which it estimates will execute 4+10 whereas in development at the same junction it's not using any resources.

Where can I look to determine why the same statement is producing such significantly differing execution plans? What factors can contribute to this?