greetings today's video will be on hypothesis statements hypothesis statements are a very critical part of scientific report um it actually usually turns out to be just one sentence in the entire report but you need to really think about your hypothesis before you start doing your research and of course that's going to be before you write your report so in this video I'll be talking quite a bit about hypothesis statements so what is a hypothesis well a hypothesis is a proposed explanation for some observations that have been made okay so it's an explanation of something or relatedly it could be an educated guess okay why you think something is okay so that could also be acting as a prediction that you know if such and such then this will happen so a prediction about the future so it's an explanation a guess about the relationships between things or prediction about what will happen now something to keep in mind is that's fine for a general hypothesis but for a scientific hypothesis in science we want to test things we want to definitively find out or as definitively as possible find out is it true or is it false so that we can advance our knowledge so a scientific hypothesis must be testable it must be possible for there to be an experiment that could tested so as you design a hypothesis statements for scientific research for that type of situation you do need to make sure that it's a hypothesis that could be tested and if it's something that you're going to do in a class room for example in a chemistry class well it has to be something that you could do in that chemistry class given the type of equipments that you have available and so on so hypothesis is a testable statement if it's testable ideally it should be falsifiable it should be theoretically possible to show that it's false if it in fact turns out to be false okay and what does it do it predicts or gives an educated guess about the outcome and if you're in a science class that's probably the outcome of an experiment now let me introduce some terminology this particular video may have a lot of new terminology for you I apologize for that but it's important and you'll see these terms a lot if you read a lot of Science in English um in science a hypothesis proposes a relationship so I've already mentioned that but it's a relationship between usually two things it could be more than two but IDE you should start small and simple so between two things two factors what do we call these things well we normally call them variables we call them variables so what does a good hypothesis do a good hypothesis makes a States a relationship between two variables and one of them we call the independent variable the other we call the dependent variable I know it's very easy to get these mixed up but you have to keep track some people abbreviate these as the IV and the DV so if you see in a scientific report the IV was bum bum bum um then probably they're referring to the independent variable so the effect of the dependent variable depends on hence dependent variable it depends on or it's determines by or influenced by the independent variable so if we change the independent variable then the dep independent variable will also change change that would be a hypothesis okay so let's take a look at some more information about hypothesis statements you need to write a hypothesis statement if you're writing a laboratory report it's probably required or at least your professor will be expecting that at the end of your introduction so before the methods before the results before the discussion but the introductory section not the beginning usually the very last thing in your introductory section will be a hypothesis statement so you need to write one and you need to write one clearly well there's many ways that you can write them of course um but a basic format would be an if then statement okay so something along lines of if you change this thing this thing is what it's a variable which variable is it it's the independent variable so if you change the independent variable then if then the dependent variable will also change because the dependent variable depends on the independent variable so if we do such and such then this thing will probably occur okay that's a very basic way of writing hypothesis statements now as I've already mentioned you need to write a hypothesis in the case of science I you need to write it in a way that an experiment can be done you could accomplish an experiment that would add support to yes the hypothesis is probably true it would support the hypothesis or that it would show that no the hypothesis is wrong it's false and let me just mention here don't worry about your hypothesis being right or wrong in science the goal is to get at the truth it does not matter if your hypothesis is false that's perfectly fine that's perfectly fine um form good hypotheses test them and if it turns out they're false that's great we now know that's not true and we can move forward from there so don't worry about being right many people want their hypothesis to be true don't get invested in your hypothesis being true write a good hypothesis test it and present your results um so do make sure that when you do your experiments you'll have results that can address your hypothesis I've seen some writing where people had a hypothesis and they did an experiments that didn't really provide strong evidence one way or the other now occasionally that will happen any way way that you'll get an unexpected intermediate result but if the hypothesis was designed well and the experiment was designed to match the hypothesis then the hypothesis should lead to a nice experimental design that will support or falsify the hypothesis so make sure you're proposing testable hypothesis things for which you can really do research that you could really do an experiment that would support it or falsify it let's take a look at a few simple examples if you drop a ball it will fall toward the ground simple if then okay we have a dependent variable and an independent variable and it's very testable it's very testable I can get a ball and I can hold it out and I can let go and see if it drops I can pick it up assuming it dropped and try again and try again I can do this a 100 times I could do this 500 times I could do it a thousands times so it's very testable it's very clear okay so this is a reasonable hypothesis in terms of forming a hypothesis if you drop a rock and a feather they will fall at the same rate maybe true maybe false again don't get tied up into it needs to be true or it needs to be false just what is it you want to test what's the relationship between the variables you're interested in form a hypothesis that is testable again this is very testable I can hold a rock in one hand hand and a feather in the other and I can let go of both at the same time and see if they drop at the same rate if they drop too quickly and hit the floor too quickly I can go up on a mountain and drop them off a cliff and have a friends at the bottom of the mountain to see if they hit the ground at the same time or not I can repeat that many times it's a testable hypothesis so that's a good thing here's another example if you increase the proportion of light exposure so if you give more light to corn plants they will grow faster okay so we could test this we could measure the amount of light we're giving to corn plants and see how quickly they grow give a different amounts of light to other corn plants see how quickly they grow we could design an experiment to test this hypothesis that would support it or that would falsify it um for those of you that have um cars you might know that many cars come with something called cruise control so once you're going a particular speed you set the cruise control and then the car by itself tries to maintain that speed for you without you contr controlling the accelerator here's a hypothesis if you use cruise control then your car will get better gas mileage many people are told this but is it true I've often wondered about this myself but here's a testable hypothesis if we have access to cars with cruise control and the time and the gasoline to do it we could design an experiment to test this so here's a little checklist for a good hypothesis when you're writing a hypothesis ask yourself does the hypothesis relate an independent variable and a dependent variable okay you should be able to identify my independent variable is this my dependent variable is that you should be able to clearly know what are your two variables assuming you're doing two but as I said earlier try and keep yourself to two variables if you go to three things get very confusing very fast also as I mentioned before is your hypothesis testable if you're going to do research on it you need to be able to test it you need to be to design an experiment or design some research that will support it or falsify it okay so do think about how would you go about designing your research that will get data that helps you falsify or support the hypothesis because if you can't test it it may be a nice hypothesis but so what the point of science is to actually Advance knowledge if we can't create an experiment for it it's probably not useful so it's just even though it's a good hypothesis as a a statement it doesn't help anything in science another thing to consider is would your experiment so if you think I've got a hypothesis and yes an experiment can be designed to test it would it be safe would it be ethical so does this involve driving a car at 300 kph on you know little town roads huh you know that might not be safe it might not be legal so it would probably fall under not ethical and not safe so even though you could theoretically have an experiment to test your hypothesis you need to ask yourself is it safe and is it ethical okay and that often is not the same as is it legal but you should probably also ask yourself is it legal um and of course you want your hypotheses to be ones that you can design and experiments that is safe and ethical to do one more thing you might want to do um as you should do is once you have your hypothesis and you're sure it is testable you do know how to do an experiment or research to report it or to falsify it and that research would be ethical and would be safe ask yourself well is there a simpler way of writing basically the same hypothesis sometimes people end up with these very long convoluted hypotheses that are technically correct but they're more complex than they need to be go for Simplicity look at your hypothesis statement if it's not already very simple and ask yourself could you rewrite it so that it's simp simpler if you can then rewrite it because you want a simple clear testable hypothesis where your research can be safe and ethical to do the testing now in science you'll often hear about something called the null hypothesis and this is a special type or a special class of hypotheses and in fact in science we almost always use a null hypothesis if you're in one of your early science classes um depending on your professor they may not care if you use a null hypothesis or not you might want to check though um because many will want you to use a null hypothesis rather than a more regular or alternate hypothesis so what is a null hypothesis a null hypothesis is a proposition that there is no effect between your independent and dependent variables there's no relationship between these variables they're they're not connected so it's the hypothesis of no difference of no effect of no impact and hence it's sometimes called the hypothesis of no difference but usually we call it the null hypothesis so there is no difference so for example I'm hoping you are watching these videos in order to learn how to write better the null hypothesis would be watching these videos provides no benefits whatsoever to your writing skill I'm hoping that if we test that it will be falsified okay but that would be a no difference hypothesis so the null hypothesis States very clearly that there's no relationship between the independent and the dependent variables now why do scientists usually prefer a null hypothesis to one that says a causes B you know the null hypothesis would be a and b are unrelated well the answer is that it makes it easier to do research it makes it EAS easier to design experiments for testing the hypothesis because if we have a null hypothesis and we test that hypothesis it can be found to be false very easily so if I say that a is not related to B and I do research on a and b and find they are related I can with conviction say the null hypothesis is false if the null hypothesis is false then it must be true that there is a relationship we might not yet know what the relationship is how strong the relationship is if it's a causal or an indirect relationship but if we can falsify a null hypothesis we've proven that there is a relationship and that allows science to move forward more quickly so null hypothesis are generally preferred in science because we can test them find that they're false which actually ends up supporting the conclusion that there is a relationship between the things that we were looking at okay let's take a look at a couple of examples the rate of corn plants growth does not depend on the proportion of light exposure so it's kind of similar to the example I gave a few slides ago but in this case it's written as a null hypothesis so I can do research with corn plants and if I find that in fact light exposure does have a relationship with how much they grow I can say this is false and that therefore supports the idea that light exposure does have an impact on corn plants growth here's another example hyperactivity is unrelated to eating sugar many people believe that particularly children but some adults as well that if they eat a lot of sugar they get crazy you know full of energy and wild can't sleep running around fidgeting um well is this true or false well we could do an experiments on this but if our hypothesis is hyperactivity is unrelated we have a null hypothesis that's much easier to falsify than a regular hypothesis so this would be the preferred hypothesis in research looking at sugar intake and hyperactivity levels so um take a look at the following examples and I want you to ask yourself is it a good hypothesis for scientific purposes consider this one ultraviolet light so UV light UV light may cause skin cancer is that a good hypothesis my answer is no it's not it may cause it it may not it's very wishy-washy would be the informal way of describing it in English it does not give a clear relationship between the two variables we have two variables but we do not have a clear link it may it may not it's just too iffy it does not give a clear um statement of a causing b or a not causing b or a being unrelated to B so this one I don't consider to be a very good hypothesis how about this one UV light causes skin cancer think about it is this a good hypothesis my answer this is better than the first one but it's still not really very good so we have two variables we have the UV light we have skin cancer so we've got two variables um the skin cancer is dependent on the UV light so our independent variable is the UV light skin cancer is our dependent variable um but we have it it causes it so I'm thinking what would my experiment be well I might go to a window open the window on a sunny day and stick my hand out outside and then take my hand back in and look and see do I have skin cancer huh no skin cancer this is going to be a very hard one in terms of testability and probably even if UV light does cause skin cancer lots of tests will fail and show no skin cancer so this is not a good hypothesis for science because it's not really testable at least not easily testable let's try another version if skin cancer is related to UV light then people with a high exposure to UV light will have a higher frequency of skin cancer how's this good or do we still have problems take a look think about that my answer answer this is definitely better than the prior to we have an if then statement we have independent and dependent variables we have a relationship specified it's very clear and I could easily imagine designing an experiment or a research that would in fact address this so this is usable I could use this I could design research based around this hypothesis but it's not a null hypothesis and null hypothesis Es are easier to work with so how about this fourth and final example UV light exposure is not related to the incidence of skin cancer that's the best of the bunch we have two variables independent and dependent variables we have a clear statement and is written as a null hypothesis this would be among the four the preferred hypothesis that a scientist would want to work with in doing research on the relationship between or the lack of relationship between UV light exposure and the occurrence of skin cancer so when you are doing your hypothesis statement and you should plan your hypothesis statement you should write your hypothesis statement well before you ever design your experiments because if you don't have a hypothesis statement why are you designing an experiment the experiments of the research should test or gather data to support or refute your hypothesis the hypothesis must come before you even design your research so write your hypothesis statement down don't just do it in your head write it down make sure that it has a clear independent variable and a clear dependent variable make sure the relationship is clearly stated or better yet that it's a null hypothesis that says there's no relationship between the two then design your research so that it can support or falsify that hypothesis ideal that null hypothesis so I hope this helps you think about hypotheses and design your hypothesis statements which would appear in your introduction probably as the very last sentence certainly in the last paragraph of the introduction section of your laboratory reports so thank you for watching I hope this helped