Thanks for the quick response! The tables have been created correctly and can as such be found in the database, but furtheron, WP Statistics is referring to them with an INCORRECT prefix (and doesn't collect statistical data either, I verified that in the tables within the database). I have not the slightest idea where it's coming from, this string is not contained in any of my WP-related sources or as far as I can see, in the database.
EDIT: I found where the error is originating from. One other Plugin I'm using (WP2BB, https://wordpress.org/plugins/wp2bb/) includes the main configuration file of PHPBB, config.php, which also contains a $table_prefix variable - that seems to overwrite it for your plugin. When I deactivate the other plugin, 'WP Statistics' is working fine. However, I'd like to use both! ;-))
The interesting thing is: doing a quick search through the code, I found that WP just as a few other plugins are also using a seemingly global $table_prefix variable, but I never had any problems (also using the aforementioned PHPBB-related plugin) before, so they seem to handle it differently than your plugin.