第四堂課翻譯

To do such an experiment. Scientist set up two groups. one is an experimental group in which a chosen variable is changed in a known way and the other is a control group in which the chosen variable is not changed. with proper experimental design,any difference between the two groups should result from the variable that was changed in the experimental group.
做這樣的一個實驗。 科學家建立兩組。 一是實驗組， 一個選擇的變量被以知名模式改變並且另一個是被選擇的變量沒被改變的對照組。 用適當的試驗設計，在兩組之間的任何差別應該起因于被在實驗組裡改變的變量。