Significance, P values and t-tests

P值表示的是概率上的显著，而不是生物学上的。

很多科学家都会使用统计检验来确定一项观测值是不是统计显著的。很多检验都会使用P值来作为一个结果是否偶然发生的一个测量度。

为了能在生物学的背景下对观测到的现象做一个正确的判断，我们必须明白P值告诉我们的是什么，以及我们如何解读它。这个月，我们将进一步说明统计显著性的概念，还有单样本的T检验。

 To help you understand how statistical testing works, consider the
experimental scenario depicted in Figure 1 of measuring protein expression level in a cell line with a western blot. Suppose we mea- sure an expression value of x = 12 and have good reason to believe (for example, from past measurements) that the reference level is m = 10 (Fig. 1a). What can we say about whether this difference is due to random chance? Statistical testing can answer this question. But first, we need to mathematically frame our intuitive understand- ing of the biological and technical factors that disperse our measure- ments across a range of values.