For one thing, they are reliable and so far as they are based on unbiased samples.
2017年12月六级真题(第二套)听力 Section C
柯林斯高阶英汉双解学习词典释义
ADJ-GRADED
无偏见的;不偏不倚的;公正的
If you describe someone or something as unbiased, you mean they are fair and not likely to support one particular person or group involved in something.