The practitioner must act if there's even one. For the researcher, completion of the report is the outcome, and it's a great success if the results are widely published. For the practitioner, effective case-management is the outcome and usually, it's a great failure if the results are widely published. Researchers have lots of time to ponder variables and test ideas. Practitioners are most often dealing with an emergency.
Research never ends, but for practitioners, the opportunity to consider options does end.
Researchers pull a single piece out of the puzzle and study it intensely, while practitioners have to work with the pieces in place. Researchers find rushing objectionable. Practitioners find delaying objectionable Practitioners have to make case-management decisions today, and every day, on topics that don't always lend themselves to traditional statistical research. Protectors cannot test whether a president is more likely to be shot if security coverage is withdrawn, because the risks of the experiment outweigh the value of the knowledge to be gained. Clearly, research into human behavior substantially advances our knowledge, but not because the numbers come out this way or that.