ab测试：ConnectionTimes(ms)表中的mean[+/-sd]是什么意思？

Question

请问如下图中的[+/-sd]列是什么意思？十分感谢。

Answer 1

1. mean-> 平均值

2. sd->standard deviation->标准偏差

What makes this value interesting is the fact that ab provides the standard deviation of the value in the third column. The standard deviation is a means to judge how accurate a particular test result is. If the standard deviation is large, then this is an indicator that something wasn't working as it should, for example, the webserver was under high load or there was a network lag. If this is the case, you will usually see that in the table at the bottom (percentage of the requests served within a certain time) the last value is much larger than the first one. In this case you should investigate your experimental setup and try to reduce the standard deviation.

谷歌翻译:

使这个值有趣的事实是，ab提供了第三列中的值的标准偏差。 标准偏差是判断特定测试结果的准确程度的手段。 如果标准偏差很大，那么这是一个不能正常工作的指标，例如，网络服务器处于高负载状态或网络滞后。 如果是这种情况，您通常会看到底部的表格（在一定时间内提供的请求的百分比），最后一个值比第一个值大得多。 在这种情况下，您应该调查您的实验设置，并尝试降低标准偏差。

简单的来说mean和[+/-sd]是两行数据......，mean就不说了，[+/-sd]就是判定你的测试误差的大小，太大说明不太好＝＝ 比如第一次请求才50ms，第二次请求竟然长达1s，这样的数据的平均值意义也不大对吧～
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