A request is considered an outlier in EUM when the EURT (or FET, if the EURT is unavailable) is greater than 5 times the stall threshold. This has an undesirable effect in that a few outlier data points can skew the metrics significantly.
For more info regarding stalled values in EUM, kindly refer to:
https://docs.appdynamics.com/display/PRO44/Configure+Browser+RUM+Performance+Thresholds
Note: For outlier requests, EUM doesn't create browser timing metrics and browser snapshots, but these requests are still sent to Analytics.