 Good morning all, today I will be dealing about research designs or epidemiological methods. So research is known as epidemiology when it occurs among a group of people. So epidemiology we can split the word epidemiology as epi, demos and ology. So epi means distribution, demo means people, we know demography and ology is study. So the study of distribution of something in a group of people is epidemiology. The research is we are searching something again and again. So commonly there are few methods to conduct a proper epidemiological study. So when we come across a problem which occurs among a large group of people we need to do a epidemiological study. So there is fundamental difference between an epidemiologist and a clinician. Clinician is people go to a clinician for getting a checkup or getting a treatment for a particular disease that is an individual, an individual going to a doctor for get a treatment. So what happens when many people are affected with the same disease just like we are seeing the corona or COVID-19 disease. So doctors cannot actually solve the problem. So what happens is epidemiologists go to the public and treat the disease. So what they do is they conduct a study and they find out how it distributes and where it is getting distributed and what is the time, place and person distribution and they solve the problem. That is all about epidemiological method. So when to conduct epidemiology and how to conduct epidemiology? So it depends on the disease. So basically we know prevalence of anemia. We have seen leptosporosis, we have seen low birth weight, there is factors and a conventional suture or stapler which is used for suturing the wounds. So all these are different problems and all these four are to be dealt with different epidemiological studies or epidemiological study designs. So basically a research design or epidemiological study, research and epidemiology is almost the same. The research is we are trying to find out a new solution or a solution for a problem. Epidemiology is the problem occurs among the people. So basically the designs are divided into two, the observational and experimental. It is very clear that one is just an observation and one is an experiment. So when a clinician is treating a particular patient and epidemiologist treating a group of people or a mass of people, clinician treats the patient within the clinic or within the hospital whereas epidemiologists go to the public and treat the disease. You cannot treat a single patient, you have to find out how the disease spreads, where it is getting started. So all this you have to find out and treat the disease and only the disease will be cured from a mass of people. So observational is an epidemiologist just observing the situation and finding out a solution. It is just like our coronavirus. COVID-19 disease, we are not treating the disease by applying any medicine or a vaccination. We are observing where it is getting spread and how fast it is getting spread. So we are asking people to go for a lockdown. So there are lot of things involved in observation study but the epidemiologists will not do any purposeful intervention from his side. So we will be just an observer. But whereas in experimental, the clinician or researcher or epidemiologist will do an intervention from his part to find out the cause of a disease or find out the effect of a particular drug. So clinician or researcher or epidemiologist will have a significant role in experimental study whereas in observation study he just act as an observer but still find out the solution of the problem. So under observation studies we have the major divisions, one is descriptive study and one is analytical study. So in observation study before that we need to find out a problem. Suppose you imagine a cholera outbreak in your city. So cholera outbreak must have started from a sewage containing water supply and lot of people are getting affected. So you are appointed as an epidemiologist and you are going to the location and you are finding out the disease, you are finding out the people, their symptoms and you are trying to find out where it is started and how it is getting distributed which all groups of people is getting affected. And finally you are making a hypothesis. Hypothesis means an assumption, your doubt without any evidence, without any proper evidence. The data which you collected by asking questions, how, when, where, you ask many questions related to the cholera, what are the symptoms, where it started, how it started, who all are affected. All you ask and make a hypothesis, make an assumption and you could say that a particular restaurant or particular pump or particular common tap is the, is, you cannot say is, it could be, it should be an assumption, could be the source of infection and these many people are affected. So drinking water from this pipe or drinking water from that particular hotel could be the cause of cholera. So you are making a hypothesis. That is a descriptive study, basic, it's a basic thing. The first study should be descriptive study in any epidemiological design. So you have a data that is, the cholera is caused due to drinking water from that particular pipe, a common pipe. But you cannot say that the cholera is due to that disease. To say that you need to test the hypothesis which was made in descriptive study. So testing hypothesis you have to do analytical study. So from the data you need to compare the data. So when you do analysis on the data with a comparison group that is known as analytical study. So only after analytical study you can say that this could be the reason for that particular disease. So these are the basic observations that in both case the ophthalmologist is observing it, he is not putting any extra intervention from his spot. He is just observing. One is making a hypothesis. So we will be seeing some of the descriptive study design. So you can see an article, a study of acute vision loss and postpartum period. And HIV associated meningitis people. So it is something like description of a certain condition. So it is known as a case report which is just a descriptive study design, one of the descriptive study design. The next one is pneumositis, carinine pneumonia and necrosis of candidiasis in homosexual men. So it has become case series. Case series is nothing but a compilation of many case reports. These all are descriptive patterns of a study. They are just describing a certain condition in a few people or a group of people. The next one is the prevalence and determinants of hypertension in a group of people. This has become cross-sectional study because the people will be asked questions only at one point of time. There will not be any follow up still. They are asking only questions, only the reports will be checked and data will be collected. So these are and one more thing which I left out is longitudinal study. So the same cross-sectional study is being repeated or if there is a follow up the same group of people is asked questions after a period of time that will become longitudinal study or follow up study. So in all these studies that is case report, case series, cross-sectional study, longitudinal study. We are just describing a condition of people and we are trying to create a hypothesis. We are not trying to analyze anything out of the data but we are just seeing the data and we are creating a hypothesis. But whereas in analytical study which is also part of observation study we can see that there is one study design which is known as case control study. We will be dealing in detail about all these study designs, case control and cohort study. But as of now case control study is nothing but analytical study. So in all analytical study that is in case control and cohort we are trying to test the hypothesis. So there will be always a comparison group. The only testing of hypothesis is possible. So in this case that is control group will be there. So this is the comparison group. So risk factors of development of color or carcinoma. So these are the patients and we will be taking one group of people without the disease that is without the color or carcinoma and we will be comparing the risk factors and we will try to find out or we try to test the hypothesis and reach into a conclusion. So this is case control study. This is always a retrospective study. We are going back. We will be asking questions or we will be taking data from the previous records. But this is one of the famous study the Framingham Hart study. This is a cohort study. This is a forward looking study. This is the study goes to the future. Okay. This study started dated back to 1948 and the study is still going on. So this is known as cohort study. Cohort means a group of people who shares common characteristics. So people with cardiovascular disease there risk factors will be assessed in the future or their risk factors will be assessed at frequent interval of time. We will not be asking questions and we will be taking data from their previous history. Instead we will be checking data, we will be collecting data from the follow-ups. Once the study started we will keep follow-up at regular interval and we will be collecting data. So such study is known as cohort study and in cohort study also there will be a comparison group. People who is not developing this cardiovascular disease. At the beginning of the study cohort study there will not be any disease in the cohort group. Over the period of time few will develop the disease and the other will remain as a comparison group. It is little complicated. We will deal this later but right now we will just check the concept cohort means a group and at the beginning of the study there will not be any disease in the group and over the period of time the cohort will be divided into two that is disease and non-disease and we have a comparison group that is non-disease and we will be comparing this and we will be comparing the risk factors. Whereas in case control study the study is started with case. Already cases are there we just need to find out some controls age and gender match controls and we will be comparing and we will be checking the risk and we will be testing the hypothesis. So the analytical study has basically two parts that is two components one is case control study and cohort study. Case control study means we will be doing on the cases and we will be taking controls. Cohort study we are doing on a group of people those people have not developed a particular disease yet they might have the disease suspected disease in future. So cohort study is always very time consuming, very expensive, very administratively complicated whereas case control study is very simple we can conduct it very easily because case is already there we just need to find out the control and conduct study whereas in cohort study sometimes the cohort will not turn into two groups over a particular period of time so it might take us to complete a cohort study. But always cohort study is better than case control study. So our study designs has become like this observational and experimental and descriptive study and analytical study. Descriptive has four parts our four designs case report series of case report that is case series cross sectional study population will be taken only at one point of time longitudinal study the same group of people will be followed up to regular intervals over a future period. In analytical study where the hypothesis will be testing there are two components case control and cohort study case control is retrospective cohort is prospective study in case control cases are already there we need to find out the controls age and gender matched controls in cohort study the cohort group will not be having any disease at the beginning of the study over a period of time it might develop into a disease or non-disease in both the study designs we need to have a comparison group in case control study the control group is our comparison and cohort study there will be a non-diseased group for comparison so finally we'll be testing the hypothesis and we'll be doing a risk estimation so all this risk estimation will be dealing in future classes so the experimental study design the in the beginning I have told you the basic two designs are observational and experimental so far we have completed observation study and observational study descriptive and analytical where the researcher or epidemiologist is just observing the condition or the decision whereas an experimental study design the clinician or researcher has a significant role or a intervention purposefully on the people or the study subjects so you can see that a study a comparison between test fluorine and proper fold in improving the laparoscopic sleeve gastrotomy in this two group of people are getting two different drugs case all these drug trials will be experimental study because two group of people the researcher are giving two different group of medicine to different group and finding out their outcome and comparing this and trying to find out which drug is better in observation study there will not be any such thing any intervention any manipulation from the part of research or an experimental study there will be manipulation or intervention from the part of research that is two different drug will be given to different groups and will be checking the outcome of the disease outcome of the medicine on the disease so this is known as randomized control trial the important part is trial trial means the investigator has a significant role so control means there will be always a controlled group in this study randomized means the groups will be randomly selected the participants will not be knowing which group they are going to participate there will be randomly selected or allocated to the groups so that is about randomized control trial so in experimental study we have two designs randomized control trial and non-pantomized trials in non non-randomized only the differences the participants are not allocated randomly they'll be knowing which group they are being being by which group they are getting allocated to or getting participated so always the randomized trial has a better advantage than the non-randomized okay so all these study designs will be dealing in detail in later classes so this is all about the promo gico study design this is a very broad classification the first division is observational and experimental and observational where the clinician has just an observer descriptive and analytical this is testing hypothesis sorry this is creating hypothesis in descriptive and analytical this is testing hypothesis in descriptive we have case report case series constitutional longitudinal study designs in analytical we have case control and cohort studies whereas in experimental study we have randomized trial and non-randomized trial this is a very broad classification but this is apt for to understand the basics of a pachromological studies so will be dealing in detail about the study within in future classes thank you