It is not science because there isn't an entirely correct way of doing it, there are no equations that will constitute efficiency or effectiveness for sure. Science is all about facts, a scientific rule is one that works all the time. Although administrators use scientific laws, techniques, and data, they do so in ways that give individual imagination and temperament free rein. There is no precise formula that will invariably work best in all administrative situations. Not only do situations and people vary, but ideas for handling them are almost as infinite as the human mind.
Public administration shares traits with arts but is not an art itself. Administrators work in highly imaginative ways, employing a mix of methods, including intuition. Like painters and composers, administrators often find their own moods and personalities reflect their work. There is however a vital difference that separates administration from being a craft and not an art. Artists create aesthetic works: administrators attempt to solve problems. The end products and criteria for evaluating the two differ. Note: There are comments associated with this question. See the discussion page to add to the conversation 1) Public Administration falls into the methodical administration performed on the basis of scientifically proven methods and approaches
2) Formed upon the basis of Statistics, Psychology and logical conclusions
3) adheres to the three laws of Motion
As all three above are scientific ; it is safe to conclude that PA is a science.