P值的大小代表什么？

统计问题（26）：

当卫生局在一个社区进行了基于团队策略的麻腮风（麻疹，腮腺炎，风疹）疫苗的推广。结果发现，接种率在两年内有所提高，与两年前相比具有统计学意义，单侧P值小于0.01。关于P值对本研究结果的意义，下面哪一项说法是正确的？

Question

When a health authority introduced a new community based vaccine promotion team, vaccination rates for the MMR (measles, mumps, rubella) vaccine improved over the next two years. The improvement was statistically significant, with a onesided P value of less than 0.01. Which of the following, if any, are true?

a) Confounding is unlikely because of the low P value

b) If the vaccination rates were varying randomly over time then the probability of a result like this or better would be less than 1 in 100

c) The difference in vaccination rates is likely to be important

d) The team approach can be recommended as better than the old approach

Answer

The P value assesses only the play of chance and gives no information about bias or confounding. The importance of the result depends on a clinical judgment of the effect of the absolute magnitude of the change in vaccination rates. This is not reported in the question and is only one component of the calculation of the P value, the others being sample size and standard deviation. The decision to recommend one approach over another should include several other considerations, such as benefit, harm, acceptability, and costs. Answer b is a fair representation of what the P value describes.

中文解释：

P值仅评估机会大小，不提供有关偏倚或混杂的信息。

结果的重要性取决于对疫苗接种率变化的绝对幅度的影响的临床判断。P值仅仅是一份报告的一部分结果，其它比如样本大小和标准差也应该报告出来。

是否推荐一种方法，还应包括其他一些考虑因素，例如收益，损害，可接受性和成本等

所以答案是选择 B

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