 Hello everyone, welcome back to another session in dentistry and more today we have a different topic hypothesis. It's not much important in undergraduate but sometimes you can expect a question like null hypothesis or alternate hypothesis but it's very much important in postgraduation while doing thesis or short study. So this video is about the classification of hypothesis. So I'll be explaining one by one with help of an example. So before moving to the classification, we need to understand the very basic idea of hypothesis or a study. So in any study we'll be having two variables. The first one is independent variable and the second one is dependent variable, okay. Independent variable which is the course and dependent variable which is the effect. So always a study will be analyzing or finding out the relationship between independent variable and dependent variable. So we take an example of smoking and lung cancer which is a cliche example of our hypothesis or research. The smoking causes lung cancer. So all of us know smoking causes lung cancer but lung cancer can be caused by many but smoking has so much significant contribution to lung cancer. So this is a cause and this is an effect. So first of all we need to understand this concept that is what is the independent variable and what is dependent variable. So independent variable, a variable which is acting like a cause and dependent variable which is acting like an effect. Now let's move on to the classification. So before that I forgot to tell you what is exactly hypothesis. Hypothesis is nothing but an accurate guess. It is not a confirmatory statement. It is an accurate guess. So it is a cancer, it is an assumption. Assumption about the relationship of variable. So we need to test the hypothesis to prove that assumption. So the hypothesis might be wrong or it might be true but we need to do a research in order to prove that hypothesis. So we say smoking causes lung cancer and that is a hypothesis. We don't have any proof for that. So any study starts with a hypothesis. So at the beginning of the study we don't have any confirmatory statement. We have just an assumption or a guess. So that is hypothesis. So now let's move on to a classification. So we have many classification, simple hypothesis, complex hypothesis, empirical hypothesis, null hypothesis, alternative, directional, non-directional, causal and statistical. Among these, these are very important. The null hypothesis and alternative hypothesis. So we start any study with a null hypothesis. That is stating that there is no relationship between these two. That is there is no relationship between independent variable and dependent variable. That is in a very short statement we can say that there is no effect of smoking in lung cancer. That is null. There is no effect. Okay. No effect. That is the null hypothesis. But alternate hypothesis is exactly the opposite. So null hypothesis we denote by this. Alternate hypothesis we denote like this. So alternate hypothesis says that there is an effect. Smoking might cause lung cancer or smoking as high chance of causing lung cancer. But null hypothesis says that there is no effect of smoking on lung cancer. So most of the studies starts with a null hypothesis and with the data collected from that particular study can reject that null hypothesis and says that there is an effect or accept that null hypothesis and says that there is no effect. So that is the most important two hypothesis, null hypothesis and alternative hypothesis. So this is a very very important null and alternative. Now let's move to the other ones. We have the first one is simple hypothesis. Simple hypothesis where we state that there exists a relationship between two variables that is independent and dependent variable. That is one causes the other or we can say independent variable causes the dependent variable. So the simplest hypothesis is smoking causes or smoking leads to lung cancer. So we have just one independent variable and one dependent variable. So it is a simple one, smoking causes lung cancer. So just one independent variable and one dependent variable. Now let's see what is complex. This hypothesis as a name says it's very complex because we have more than one independent and more than one dependent variable. That is smoking and uses of drugs leads to cancer, tension and chest infection. So here we have smoking and drugs causes or leads to lung cancer, tension and chest infection. So here we have more than one independent variable that is smoking and drugs and more than one dependent variable. So it became complex that is complex hypothesis. Now what is empirical hypothesis? Empirical means it is based on evidence. So if we have evidence that is we have evidence to say that smoking causes lung cancer. That type of hypothesis known as empirical sometimes we won't have evidence such as if we take the corona pandemic we don't have any much evidence on that. But smoking and lung cancer there's a lots of cohort study which has already proven smoking causes lung cancer. So we have evidence. So if we say something or some hypothesis with evidence that becomes empirical hypothesis. Now what is null and alternative that we already discussed in detail null means there is no effect between the independent and dependent variable. So alternative just opposite sometimes alternative hypothesis also known as research hypothesis. Because if we are seeing a effect between two variables that should be a empirical one okay. So alternative hypothesis means there is already evidences present in the literature because if you are saying smoking leads to lung cancer will be a simple one it will be empirical one it will be a alternative one. Most of the studies will not be as simple as it looks will be much complicated but I am trying to give you an idea at the very basic level. So alternative is just opposite of null hypothesis where we say that there is an effect but in order to say that we need to have evidence that evidence comes from previous studies of literature. So that is a empirical one also so that is null and alternative hypothesis. So what is directional and non-directional hypothesis. So this alternative hypothesis also known as H1. So this is a null hypothesis H0 will be denoted like this. So you will be seeing in articles H0, HA or H1 this is alternative hypothesis okay. Now we have the directional and non-directional. So directional hypothesis predicts the direction of relationship between independent variable and dependent variable. Just take an example a high quality of nesting education will lead to high quality of nesting practice skills. So there is a direction. So high quality will lead to high quality practice, high quality practice. So if people with good education will definitely result in good people, I mean good nesting skill practice. So that is a direction. So we are pointing our hypothesis in a particular direction if the person is with good quality of education will be having good quality of practices that is directional hypothesis. There is non-directional hypothesis which will not predict the relationship between the independent variable and dependent variable. So the non-directional hypothesis is like there is no specific direction of the relationship. Example is teacher-student relationship influence students learning okay. So we don't know if the teacher-student relationship might increase the students performance or decrease the students performance we don't know. If the students are having not a good rapport with the teacher that might negatively affect the students performance. So it is not exactly saying a direction this is exactly saying a direction. High education high practice but teacher-student relationship influence students learning says just influencing in which direction it's not specifying that is non-directional hypothesis. Okay so that is the difference between directional and non-directional. So it all comes under different categories of null and alternative. So these are very very important. Now the causal hypothesis. Causal hypothesis means causality, smoking causes lung cancer. It predicts a cause and effect relationship or interaction between the independent variable and dependent variable. So this causal relationship is again an alternative hypothesis or again it is an empirical hypothesis because it is saying a causality that is this causes this. In order to say that we need to have evidence that is empirical. If you are saying that this causes this or there is an effect it again becomes alternative hypothesis. So that is causal hypothesis and last one is statistical hypothesis. So the statistical thing is very tricky sometimes there won't be any effect between these two variables but we might get a statistical significance because sometimes we do a study with just five people okay. We take five people who are smoking and five people who are not smoking and found out that there is a risk of four times that means there is four times risk of people with smoking to have a lung cancer and we get a statistical significance. And we put forward a statement that the smoking causes lung cancer because we have a statistical significance but does it true because we have just five samples. Even though we have statistical significance in reality we cannot say that smoking causes lung cancer because we have tested that relationship in just five people or let it be in a very small sample. So in order to prove that it should be a very bigger sample it should be a cohort study it should be studied in variety of populations variety of regions then only we can prove it or we can say that empirically or alternatively or causally. So statistical significance is just a mathematical thing we can obtain with very small sample but it doesn't prove causality. So statistical significance just says that there is an effect but in reality it won't be there. Or less chances. So that is about hypothesis. So all you need to understand is the basic idea of null hypothesis and alternative hypothesis. This is very important and rest all comes under different names of alternative mostly and the empirical the directional causal all are one or the same of alternative hypothesis. So hope you understood the concept. I'm not explaining in detail or I have not explained it in detail. I just want to give you an idea about the independent variable dependent variable concept and cost effect and the various classification. So I'll come up with a new topic in the industry and more. Thank you.