Trendline percentiles: how are they calculated

How to show the Trend Line?

When looking at you WIP in the WIP Run Chart, you can expand the controls for this chart (in red) and decide to show the Trend Line:

The below panel will appear and allow you to decide what do you want to see:

By default it will show you the trend line for the 85 percentile of your WIP for the past 10 days. You can decide to change the percentile and interval according to what you want the chart to show you.

How are the percentiles calculated?

We take the number of WIP from the last 10 days (one per day) and order them in ascending order rather than the order of days (2, 3, 3, 4, 4, 5, 5, 5, 8, 8).

For the WIP chart there is only one data point per day so there are 10 dots to use for the calculation. In the Cycle Time Scatterplot there can be many more but it generally works the same.

Then, it finds how many data points are needed from the total to reflect 85% (rounding down). 8.5 data points reflects 85% of 10 data points so it rounds down to 8.

So we find the number in the list we made that is in the 8th position - which, in our case is 5 - and it plots the dot for the trend line for today’s date at 5:

WIP: 2 - 3 - 3 - 4 - 4 - 5 - 5 - 5 - 8 - 8

Example:

If we get the below values and then order them we can easily find the values for each percentiles:

Raw values: 5, 6, 6, 7, 7, 6, 5, 4, 4, 3

Ordered values: 3 - 4 - 4 - 5 - 5 - 6 - 6 - 6 - 7 - 7

5 - 50%

6 - 70%

6 - 85%

7 - 95%