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95th Percentile Calculations

The 95th percentile is calculated for rollups, and for event and report generation purposes.

Rollups:

• For hourly rollups, the 95th percentile is calculated as a continuous percentile of the polled values.
• For daily rollups, the 95th percentile is calculated as a continuous percentile of the hourly 95th.
• For weekly rollups and beyond, the 95th percentile is calculated as a continuous percentile of the daily 95th.

Reporting:

• When the resolution is less than a day, the 95th percentile is calculated as a continuous percentile of the polled values.
• When the resolution is a day or greater, the 95th percentile is calculated as 95th of the 95th.

Example: Calculate the 95th Percentile

The following example shows how the 95th percentile is calculated, given an hour of calculation and a 5-minute poll cycle.

Follow these steps:

1. Collect an hour worth of data at a 5-minute poll cycle.

   1 2 3 4 5 6 7 8 9 10 11 12

   30 10 20 70 60 30 80 10 90 20 70 50

   Reorder

   10 10 20 20 30 30 50 60 70 70 80 90

2. Calculate the row number (RN), floor row number (FRN), and ceiling row number (CRN) values.

   The formulas for calculating RN, FRN, and CRN are as follows:

   • RN = 1+((N-1)*P)

     N

     Represents the number of polled values that were collected.

     P

     Represents the percentile value.

   • FRN = floor(RN)

     FRN

     Represents the largest integer that is not greater than RN.

   • CRN = ceiling(RN)

     CRN

     Represents the smallest integer that is not less than RN.

   The equations for this example are as follows:

   RN = 1+((12-1)*0.95) = 11.45
   FRN = floor(RN) = 11
   CRN = ceiling(RN) = 12
   

3. Calculate the 95th percentile.

   The formula for calculating the 95th percentile is as follows:

   if (CRN = FRN = RN) then
   (value of expression from row at RN)
   else
   (value of expression for row at FRN) + (RN - FRN) * (CRN row - FRN row value)
   

   The equation for this example is as follows:

   (80) + (11.45 - 11)*(90-80) = 84.5000
   

   The 95th percentile for this example is 84.5000.