We control for company size ( SIZE it ), the market-to-book ratio ( MB it ), and leverage ( LEV it ).

The STOCK i variable controls for any time-invariant differences between the treatment sample of stock-financed acquirers ( STOCK i = 1) and the control sample of cash-financed acquirers ( STOCK i = 0).

We control for this by using cash-financed acquirers rather than non-acquirers as our control group.

请问上面几句话中的control for都是一个意思吗？如何理解啊？