# Why sometime 99.99th doesn't shown

**URL:** <https://discuss.elastic.co/t/why-sometime-99-99th-doesnt-shown/272467>\
**Category:** Elasticsearch\
**Tags:** rally\
**Created:** [May 8, 2021, 9:43am UTC](https://discuss.elastic.co/t/why-sometime-99-99th-doesnt-shown/272467 "2021-05-08T09:43:30Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![GITnewfish](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/gitnewfish/32/87303_2.png) [@GITnewfish](https://discuss.elastic.co/u/GITnewfish)\
**Post date:** [May 8, 2021, 9:43am UTC](https://discuss.elastic.co/t/why-sometime-99-99th-doesnt-shown/272467/1 "2021-05-08T09:43:30Z")

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I do found sometime 99.99th doesn't shown in my summary, and sometime it shows ok.  
In the doc, it said "Rally will not show a 99.99th percentile if it could only capture five samples because that would be a vanity metric". Does this mean the rally load-driver does't receive api response and in this case the report is meaningless? And what's the meaning of "mean"?

 ![image](https://us1.discourse-cdn.com/elastic/original/3X/7/0/70d777b64c26f6fdd849cacf74d08fd49bf76ab0.png)  
 ![image](https://us1.discourse-cdn.com/elastic/original/3X/a/c/ac87c14464587d45fca892edc7b6e448f96d6e3e.png)

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**Author:** ![dliappis](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/dliappis/32/56174_2.png) [@dliappis](https://discuss.elastic.co/u/dliappis)\
**Post date:** [May 10, 2021, 4:32pm UTC](https://discuss.elastic.co/t/why-sometime-99-99th-doesnt-shown/272467/2 "2021-05-10T16:32:05Z")

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Hello,

`mean` refers to the statistical mean: [Mean - Wikipedia](https://en.wikipedia.org/wiki/Mean) (commonly known also as "average".

Regarding why 99.99th percentile doesn't show up, this has to do with the definition of percentiles and the fact that we don't estimate (interpolate) percentiles in Rally; we will **only** show a percentile value if the population of values -- also known as sample size, in this case bulk responses, is sufficient to calculate the necessary percentile.

More resources about percentiles:

- [https://statisticsbyjim.com/basics/percentiles/](https://statisticsbyjim.com/basics/percentiles/)
- [Percentile - Wikipedia](https://en.wikipedia.org/wiki/Percentile)

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**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [June 7, 2021, 4:32pm UTC](https://discuss.elastic.co/t/why-sometime-99-99th-doesnt-shown/272467/3 "2021-06-07T16:32:47Z")

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