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.

1）90%响应时间它是统计响应时间的参数，带有统计学意义，是科学性的；

2）可以这样理解，这个事务所有的运行次数中，90％的次数落在这个响应时间里；（90%的响应时间不超过XX秒）