Which of the following is not true about non randomized trial?

Ans. is 'b' i.e., Degree of comparability high Non-randomized trials o It is not always possible for ethical, administrative and other reasons to reso to a randomized controlled trial in human beings. o In such situations, non-randomized trials are used. o As there is no randomization --> degree of comparability will be low and the chances of spurious result is high. o Major types of non-randomized trials are : ? i) Uncontrolled trials ---> Control group is not used for example, effectiveness of pap test for cervical cancer. ii) Natural control (natural experiments) --3 Nature has separated the papulation in two groups for example, in respect to cigarette smoking, people have separated themsleves into two groups, smokes and non-smokers. iii) Before and after comparison study (Pre postclinical trial) These studies centre round comparing the incidence of disease before and after introduction of a preventive measures. o The events which took place prior to use of the new treatment or preventive procedure are used as a standard for comparison. o In other words, the experiment serves as its own control, this eliminates viually all group differences. o Several trials may be needed before evaluation is considered conclusive. Note : I am not sure about option 'a' as i am not able to understand this option.