Question:

How exactly does CEM calculate its baselines?

Answer: 

APM CE (CEM)  baselines are calculated based on the algorithms below. To change the algorithms, modify the parameters in the tess-default.properties file and restart the EM. APM CE uses these values for Box-Whisker graphs.

The tess-default.properties file contains the following default settings:
baseline.durationInDays = 28
baseline.upper.discardOutlierPercentage = 5.0
baseline.upper.offsetPercentage = 20.0
baseline.lower.discardOutlierPercentage = 5.0
baseline.lower.offsetPercentage = 20.0

The upper baseline is calculated as follows:

• Take all hourly maximums over the last baseline.durationInDays days (datapoints)
  • if number of datapoints = = 0 then return -1
  • outlierCount = number of datapoints * baseline.upper.discardOutlierPercentage / 100
• Discard the largest "outlierCount" datapoints
  • maxWithoutOutliers = largest datapoint left
  • return upperBaseline = maxWithoutOutliers + (maxWithoutOutliers * baseline.upper.offsetPercentage/100)

The lower baseline is calculated as follows:

• Take all hourly minimums over the last baseline.durationInDays days
  • if number of datapoints == 0 then return -1
  • outlierCount = number of datapoints * baseline.lower.discardOutlierPercentage / 100
• Discard the smallest "outlierCount" datapoints
  • minWithoutOutliers = smallest datapoint left
  • return lowerBaseline = minWithoutOutliers - (minWithoutOutliers * baseline.lower.offsetPercentage/100)

Release:
Component: APMCEM