51Testing软件测试论坛

标题: What is the 90th percentile and how is it calculated [打印本页]

作者: lotus 时间: 2006-3-17 12:02
标题: What is the 90th percentile and how is it calculated
Problem Description: What is the 90th percentile and how is it calculated
--------------------------------------------------------------------------------

Solution: The 90th percentile is the value for which 90% of the data points are smaller

The 90th percentile is a measure of stastical distribution, not unlike the median. The median is the middle value. The median is the value for which 50% of the values were bigger, and 50% smaller. The 90th percentile tells you the value for which 90% of the data points are smaller and 10% are bigger.

Statistically, to calculate the 90th percentile value:
1. Sort the transaction instances by their value.
2. Remove the top 10% instances.
3. The highest value left is the 90th percentile.

Example:
There are ten instances of transaction "t1" with the values 1,3,2,4,5,20,7,8,9,6 (in sec).
1. Sort by value -- 1,2,3,4,5,6,7,8,9,20.
2. Remove top 10 % -- remove the value "20."
3. The highest value left is the 90th percentile -- 9 is the 90th percentile value.

The 90th percentile value answers the question, "What percentage of my transactions have a response time less than or equal to the 90th percentile value?" Given the above information, here is how LoadRunner calculates the 90th percentile.

In Analysis 6.5:
The values for the transaction are ordered in a list.
The 90% is taken from the ordered list of values. The place from which it is taken is

Rounding to the small value the number: 0.9 * (Number of Values - 1) + 1

In Analysis 7 and above:
Each value is counted in a range of values. For example, 5 can be counted in a range of 4.95 to 5.05, 7.2 in a range of 7.15 to 7.25. The 90% is taken from the range of values that the number of transaction in it and before it is >= ( 0.9 * Number of Values).

This difference in the methods can lead to different 90% values. Again, both methods lead to correct values as defined by the 90th percentile. However, the algorithm to calculate these figures has changed in LoadRunner 7 and above.

转mercury support网站英文好的帮忙翻译下吧;)

作者: Dorpnight 时间: 2006-3-21 11:32

原帖由 lotus 于 2006-3-17 12:02 发表
Problem Description: What is the 90th percentile and how is it calculated
--------------------------------------------------------------------------------

Solution: The 90th percentile is the v ...

这段文字对90%的做了很详尽的解释阿，还要怎么翻译阿？

欢迎光临 51Testing软件测试论坛 (http://bbs.51testing.com/)