The phrase "greater effectiveness" means that something is better at achieving a certain goal or getting desired results compared to other options. Full definition
Our task in this volume will be to explore the ways in which religious resources may be used with greatest effectiveness in dealing with alcoholism. (religion-online.org)
One intern once showed me a research article citing the sometimes greater effectiveness of the interns when compared with the more experienced, older staff. (abetterdivorce.com)
The reason that Chinese herbs have a reputation for great effectiveness is not because of the herbs themselves. (acuatlanta.net)