'were arbitrarily selected' is correct and usable in written English.
You can use it when you want to say that something was chosen haphazardly or without a clear rationale. For example: The 20 participants for the study were arbitrarily selected from the applicant pool.
First, variables were tested variable-by-variable. Variables showing an association at a significance level of P < 0.2 were arbitrarily selected for multivariable analysis (forward and backward selection procedures).
To validate our analysis and identify novel candidate genes related to the thermogenic activation in BAT, the top 10% most cold-induced genes were arbitrarily selected for manually curated analysis.
The ten abstract pictures were arbitrarily selected from the work of renowned artists, thus their arousal, valence and dominance scores were assessed for the first time in the current work.
"Some of our members protested after they were left out and people were arbitrarily selected to go into the event, we refute any involvement with what took place beyond this".
The parameters used for each Equation were arbitrarily selected.
Only the variable lengths of the regions were arbitrarily selected (cf. Table 5).
They are arbitrarily selected and easily dismissed.
The Dow faces frequent criticism for being arbitrarily selected and unrepresentative of the US economy.
Delaminations are commonly defined based on the pixels associated with temperatures higher than predefined threshold values that are arbitrarily selected.
Here Hcj can be arbitrarily selected without any limitation, and therefore one can always construct an acceleration Hamiltonian by only using realizable Hcj.
The shortcoming of the approach, however, arises when probability distributions are arbitrarily selected in situations where available information is incomplete or imprecise.
