求对照实验（controlled experiment）的含义的英文

题目

求对照实验（controlled experiment）的含义的英文

答案

A controlled experiment is one in which everything is held constant except for one variable.Usually a set of data is taken for a control group,which is commonly the normal or usual state,and one or more other groups are examined,where all conditions are identical to the control group and each other except this one variable.Sometimes it's necessary to change more than one variable,but all of the experimental conditions will be controlled so that only the variables being examined change and the amount or way they change is measured.
It is a experiment testing only ONE factor at a time.
Its a test of the effect of a single variable by changing it.
Controlled experiments provide insight into cause-and-effect by demonstrating what outcome occurs when a particular factor is manipulated.Controlled experiments vary greatly in their goal and scale,but always rely on repeatable procedure and logical analysis of the results.