We say two of these trials will come for real, so if you buy the products, you pay us, we will ship the product to you, otherwise you keep the money.

我们告知受试者试验中有两种商品是真实的，所以如果受试者想要购买的话，就可以付钱给我们，我们把商品寄送过去，否则钱就是受试者的。

斯坦福公开课 - 7个颠覆你思想的演讲课程节选