What is managing by the numbers? What are the advantages and disadvantages?
"Managing by the numbers" could refer to various things, so you may want to check with your text or professor to be sure you get the right definition...
One meaning of this is managing employees and processes (especially in big firms) by intensively analyzing them. Data are used to determine which employees are good at which things, who is most productive, who works well with whom, etc. Data are also used to measure the impact of every part of the production process (like UPS mapping out routes for its trucks). The data are used to determine how to use the employees most efficiently and how to streamline the processes.
The advantages of this system are that the data can be used to see trends and problems (or possible advantages) that managers cannot see by just observing their employees. This could lead to much more efficiency.
However, there are dangers. A company might try to measure the wrong things, or use the wrong metrics. Trying to manage employees this way might make them feel like commodities and lower their productivity.