做驗中, 點解有時要做對照實驗?

實驗通常係證明實驗中的某個假設
而對照實驗係支持這個假設的條件

In biological experiments,we usually set up a Control (對照實驗) to compare its results with thise of the experimental set-up. A control is a set-up that is the same as the experimental set-up ,except that it does not contain the substance or condition under study.