Why can't I get similar performance degradation with Monkey in different experiments?

I have configured experiments to test which among 10 launched apps impacts performance the most. But I can't make an objective comparison, because if I launch the experiment twice with the same configuration, I get very different performance degradation, in terms of memory occupied and launch times. This is a piece of code from one of the workload scripts. I set the seed to always generate the same events, I wipe the cache at the end of each experiment and clean up the apps before starting another, yet in two experiments with the same settings I get a memory occupancy that grows up to three times faster in one than in the other. while true; do adb shell monkey -p com.android.chrome -s 1 --pct-appswitch 100 --ignore-crashes --ignore-timeouts --ignore-security-exceptions --monitor-native-crashes -v -v 1 sleep 1 adb shell monkey -p com.facebook.katana -s 1 --pct-appswitch 100 --ignore-crashes --ignore-timeouts --ignore-security-exceptions --monitor-native-crashes -v -v 1 sleep 1 adb shell monkey -p com.google.android.apps.maps -s 1 --pct-appswitch 100 --ignore-crashes --ignore-timeouts --ignore-security-exceptions --monitor-native-crashes -v -v 1 done Is there a way to get similar performance degradation in two experiments? Is it just me doing something wrong or is this something that can't be achieved because there are too many random factors at play?