You will sometimes have new documents for translation but no TM that contains matching content. To find out whether the documents themselves contain repeated content, you can analyze them against a dummy (new and empty) TM. In this situation, however, the Analyze Files report will, by default, tell you only how many New segments and Repetitions the documents will generate during translation.
To gauge more accurately the time and effort that the documents will take to translate by checking also how many fuzzy matches the documents will generate, in the Settings screen of the Analyze Files wizard, select Analyze Files | Report internal fuzzy match leverage (as described in the earlier section, Configuring the settings).