以偏概全

yǐ piān gài quán

to generalise from a part

Character by character

以yǐ
with

偏piān
the partial

概gài
cover

全quán
the whole

只看一两个例子就下结论，是以偏概全。

Drawing a conclusion from one or two examples is generalising from a part.

Tone: negative (criticism).

Learn this in Lesson 108 · HSK 7–9: 怎样把道理讲清楚 (Building an argument)

A dialogue, a reading, word cards with audio and a drill that uses it, in Learn Chinese with Bao. The first lessons of every level are free.