# How is 95% response time calculated in visual studio load test

We were analyzing VSTS load test report and we fond response times for an endpoint is given here

avg response time :- 0.57

90% response time :- 1.06

95% response time :- 1.23

99% response time :- 1.46

As per VSTS recommendation the sampling rate is set to 15 sec. We are using VSTS cloud offerings to generate load.

As per performance graph (in results) response time peaks shown are at approx 0.6 seconds and nothing above that.

When we are downloading samples we can see all entries(1 entry per 15 seconds) have data matching with what is plotted on the graph and is less that 0.6 seconds.

Our SLA is to support 1 sec for 95%. Now we can not understand

how are 90%, 95% and 99% response time calculated ?

how to get more data about the requests which contributed to 95% response time so that we can debug

Please help us.

Thanks in advance.

## Comments

For each different counter, one value is generated in each sampling interval and that value is shown on the graphs. Hence the graphs often seem to omit peak values. The tables of results collect all the values and the percentiles for response times are calculated by excluding the slowest values. If a total of N response times are collected then the 90th percentile excludes the slowest 10% of those N times, similarly for the other percentiles. To understand the range of response times compare and contrast these values:

The percentiles.

The average. But remember the average can be distorted by a few very large or very small values.

The median. Which is found by excluding almost half of the slowest values and the same number of the fastest values.

The minimum and maximum values

Microsoft have several web pages about analysing load test results. This page is one to start with.