A quasi-randomised trial is one in which participants are allocated to different arms of the trial (to receive the study medicine, or placebo, for example) using a method of allocation that is not truly random.
Allocation might be based on date of birth, medical record number, or the order in which people were recruited (for example, every other person might be allocated to the placebo group).
With quasi-randomisation there is a greater risk that the investigator will be aware of which participant is in which group. There is therefore a risk of selection bias.
