Psychometric tests determine the suitability of your character for a career.
Police forces use Psychometric testing to test for empathy. If you have empathy you won't have a career in the force. Empathy is counterproductive to a satisfying career in the Police.
Psychometric testing is hard to study for. You are asked the same question in numerous different ways several times in the testing. It's hard to be consistent if you're"faking" (or misrepresenting) your answers.
As one of my pervious managers told me before my (successful test) , be honest in the test, after all if you're not suited to the role, aren't you better persuing another career?