 Welcome back to my classes on Epidemology, so today we are seeing about blinding. So what is blinding and how blinding helps to prevent the biases. So last class we had seen various types of biases, biases which are seen in case control and cohort study. So the most commonly biases are seen in case control and cohort study are very rarely experimental study because in experiment we are keeping both participants in random way and in both groups of participants we are allocating by random methods. So the group itself is comparable, the group itself are not using any bias. The selection bias is completely removed from the study design, that's why it is the most powerful study to prove hypothesis or prove and cause effect or the association between a cause and effect. So exactly what is blinding and blinding is not only possible in case control or cohort study because the study, case control study, the participants will be definitely knowing their cases or their controls because people with diseases they will be knowing their cases and people without the disease will be knowing their control. So that is an inherent part of the study design that bias cannot be eliminated in any way. The cohort study also after a period of time they will be realizing they are becoming exposed group and the other group is not exposed. So some part of the bias or some types of biases are unavoidable but the main bias selection bias is completely removable or avoidable in experimental study because of randomization. So mostly this randomization is possible only in trials. So as I mentioned in experimental design, the study designs randomization is possible only with drug trials or any new machineries or any new techniques, any comparison of new and old techniques. In such scenarios we can do blinding or in any case study because of the cases and such scenarios are ethically involved. So we cannot keep any random allocation. So let us come to the topic blinding. So blinding in clinical trial is as the name suggests it is the concealing or masking the treatment regime or treatment allocation that is nearly trial we have basically two groups. One is treatment group and one is control group or the two groups will be getting two different treatment or two different drugs, one new trick and one old trick. So the idea of blinding is the participants should not be knowing which drug they are getting or which group they are allocated to, whether they are being allocated to the treatment group or control group they should not be knowing that is a basic idea of blinding. The participants will not be knowing which group they are going that is allocation concealment so that is we do by randomization but which drug they are getting we can do only by blinding because we have to make sure that the participants is not have any clue about the intervention being right. So there are basically three types of blinding single blind double blind and triple blind studies the most commonly used is double blind studies. So blinding refers to keeping the trial participants that is the first group they are the participants they get the intervention the investigator they are the people who give intervention or they are doing the manipulation or intervention they are the investigators or the usually the doctors or any other clinical trial people and the third part is assessors those collecting outcome data they'll be checking the measurement if you are trying a drug on blood pressure so they'll be checking blood pressure before and after the study. So we have three groups in any type of study that is first one is participants second one is investigators and third one is assessors okay so in blinding we have to blind one or three groups of these participants I mean these categories so that becomes primary I mean single double or triple blind study so they should be unaware of an assigned intervention they should not be knowing which what type of material they are getting and what is the intervention they are being allocated to nothing they should be knowing so it actually prevents bias so the one bias we had seen in case control studies hot on effect observer bias when they are being known as case or they they know that they are being watched under study they'll automatically psychologically change the so that will be eliminated because they don't know which group they are being allocated they know that they are just part of the study but they don't know which group they are being allocated and another bias was investigator bias the investigator who knows hypothesis and who knows which group is getting which intervention so such bias also will be eliminated so investigator means in case control and it is about hypothesis but in experimental it is about intervention okay so blinding basically prevents bias so bias is something which distorts the result of any study so we have only three types first one is single blind study so we can see the picture okay this is a open trial where the first category that is participants or patient next healthcare providers or investigator that is staff and the analyst people who measure the outcome data that is VP or anything all are open to know the intervention so that is a open trial so the single blind trial the participants they don't know which they don't know which drug they are getting or which type of intervention they are getting okay so allocation concealment is different and blinding is different allocation concealment is they'll be allocated to different groups by random checking or randomization so this blinding is the participants will be blinded to the treatment intervention or the allocation or not allocation the particular intervention they are being given so here the patient is blinded or the participants is blinded okay that is a single blind study it is the one of the three categories that is participants rather than investigator usually we get doubt whether the participants or the investigator is blinded usually it is a participants okay that is single blind trial so when we come to double blind trial what happens is this is a double blind trial here the patient that is a participants and the staff or the investigator both are blinded both groups they don't know what they are doing what intervention they are giving to what group they are giving they don't know anything about the studies okay so this is known as a double blind trial so double blind trial participants and the investigators usually remain unaware of the interventions okay that is a double blind trial so triple blind trial is nothing but the double blind plus the analyst okay so all the three categories will be blinded the participants the participants the investigator and the outcome measure people that is analyst or the assessors are blinded so it is a double blind trial that also maintains a blind data analysis can say that the outcome measuring people or the data analyst the person who is doing that analysis so all the three categories of people are blinded here so this is triple blind study okay so most commonly you study is double blind study rather than triple blind because the triple blind study usually needs a very laborious framework because the participants has to be kept very cautiously they have to be blinded the investigator has to be blinded and again the assessors or analysts to be blinded then there should be another group of people who'd be doing majority of the other works they have to do the allocation they have to give the treatment they have to make sure they have to do the outcome measure so there'll be four groups of people in this study so usually will be the double blind study is most commonly happening triple blind studies quite rare in our trials so this is all about blinding so blinding is basically about preventing bias the least bias reported studies experimental study which is most trusted or it is at the top of the evidence based just under meta-analysis and systematic reviews so it is the best study to prove causality or association so blinding is must in any type of trial so usually allocation concealment and blinding is different allocation concealment is the allocation of participants will be considered blinding is different thing the intervention is must so blinding is also known as masking so we have three type of blinding single blind double blind and triple blind single blind patient or any participants blinded double blinded the investigator also will be blinded and the triple blind of commission and analysts also