I'm here okay so this one would be the null this one would be the null hypothesis the one that has equal two and this one would be the alternative hypothesis H a that's going to be a greater than alright that does not have an equal to part everybody okay there so you write down the claim write down the opposing view then decide what's the null and alternative I always told my students don't write H 0 and H a on your paper don't write your two opposing views and then decide what's the null and alternative all right let's look at the next one here all right we have mu as mu is less than 98.6 I'm going to give myself a little more room here okay that was what I thought what they think is true and it's actually lower than 98.6 but what was the opposing view many people thought that the population mean average normal body temperature is 98.6 right again they never they never said they thought it was higher they just thought it was is 98.6 that sounds like the opposing view is just equal to so I'm gonna go with mu is equal to 98.6 everybody okay there so so look I got my claim what they thought was true and then I have my opposing view from the from the article that kind of gives me an idea of what there may be what they're thinking was in terms of the opposing views if you noticed by the way the the null and alternative hypothesis don't actually have to be true mathematical opposites this one's less than and eat this one's equal to now I can decide what's the null and what's the alternative remember claim has nothing to do with it right we're looking for MU equals 98.6 any statement with equal is always a null hypothesis so we're going to write h0 next to that one this one and last and remember less than points to the left so again that's going to be in and alternative hypothesis alright let's look at the next one so this one has only had one statements they entered IQ tests have a population mean of 100 may rewrite that so I have more room here so mu was equal to 100 and that was my claim okay there's my claim all right so huh I don't have the opposing view so now I gotta think about opposites right well what would if this was false right if what the article said about IQ test if that was false what would be true well the opposite of equal to is actually not equal to so this is very classic if you ever get an equal to claim the opposite of an equal to would be different or not equal to so it looks like an equal to with a slash through it so we're gonna write the opposing view as not equal to 100 notice I'm not gonna say it's greater or less I'm just gonna say it's different right not equal to 100 again claim has nothing to do with it all right claim does not decide what's the null and what's the alternative claim is just what if the person think is true or what do they say in the article all right this one better - okay so what did we say the null hypothesis is the one with equal to so which of these two have equal to of course the top one that's got to be the null hypothesis so I'm going to write h0 next to that this one does not have an equal to part so this would be H a pretty okay it's actually not too bad once you kind of get the steps the main thing again is wait to write don't write H 0 and H a on your paper write your claim write the opposite of the claim then figure out what's the null and alternative hypothesis and it goes by the sign okay now these actually go with a certain type of test so one of the things we like to know is what type of tests were dealing with H a always decides the test a chain does not h0 not the null hypothesis the alternative hypothesis decides the test anti-fascist testing we're often trying to reject the null hypothesis if we were able to reject the null hypothesis then we're sort of supporting the alternative hypothesis in other words the H a is the one that sort of decides the test so if you kind of remember this is kind of my easy shortcut for one and two population hypothesis test if you have a less than well less than it looks like an arrow like an the tip of an arrow pointing to the left so this would be considered a left tailed test if your H a is greater than greater than it looks like an arrow pointing to the right so this would be considered a right tailed test now if you're not equal there's sort of two ways of not equal to could happen it could be greater or less so not equal actually involves both tails so we sometimes call this a two-tailed test now this really only applies for one and two population hypothesis tests once you start getting into multiple population like if you have a ten population hypothesis test a lot of tests they condense it down into one sort of right tailed hypothesis test things like an ova and the goodness of fit test things like that but for one into population you'll have this left tail red tail and two tail all right so let's see what kind of test these examples work remember it's H a that decides not claimed not the null not h0 right H a the alternative hypothesis decides the test so look at this one our H a was greater than well greater than points to the right so this would be a what a right tailed test right tailed test I tailed test all right how about the next one HHA was less than less than looks like an arrow pointing to the left remember it's not the claim it's a CH a sign that tells you whether H a is the claim or not sometimes people say something that's a null hypothesis sometimes people say something that's an alternative this one's going to be a left-tail test and it's like a little arrow pointing to the left so we're going to go with a left tailed test here okay and now we have this one now this one the H a was not equal remember don't go by claim don't go by the no go by H a what's the symbol in H a well it was not equal so this is going to be a two-tailed test so we'll see later that p-value and test statistic calculations are going to fall in the right tail for this test calculations are going to fall in the left tail for this test and we have to consider both tails in calculations when we do this test so it is important that you know what kind of test you're dealing with now again you may see people occasionally write this as like instead of equal two they might write less than or equal to I kind of prefer just to write equal to there especially since it's said equal to in the problem so I really wouldn't want to change this to less than or equal to and same thing with this one it actually said that it was equal to 98.6 or people thought it was it's at one point so I think I would leave it as equal to though sometimes you'll see some teachers say that they would they want these to be mathematical opposites of each other so they might write greater than or equal to here but I think I would prefer again equal to there now remember a couple things member to leave the letter on the left and the number on the right when you write this less than points to the left greater than points to the right now if you tell them with a two population problem a lot of times what you want to do is label what's Group one and what's group two so if it said group population one is higher than population two you might write something like this pi one is higher than pi - all right and always write population one on the left and population two on the right when you do this we'll get more into this when we get into two population tests but basically you want the population one on them on the right and population two on the left greater than again would be an arrow pointing to the right if we are doing a less than maybe the population mean average for group 1 is less than group 2 we might say something like mu 1 is less than mu 2 okay the population mean average for population 1 is less than for population 2 notice again I put Group 1 on the Left group 2 on the right I tend to intend to just kind of write it as they say it yeah so if they said that they think the the mean average for men is lower than for women I would just make group 1 men and group 2 women and just write it as men as men's mean averages lower than for women so I kind of tend to write it as they say it in the in the article okay all right so don't forget your steps write the claim down write the opposite or posting view of the claim and then decide what's the null and alternative hypothesis alright so this is the first step in hypothesis testing it's one of the most important because if we get this wrong everything else is going to be wrong you're gonna actually the computer is going to be calculating wrong numbers so you want to make sure you get the null and alternative hypothesis right okay because that will tell us what direction and what we have to plug into the computer alright so thanks again for joining me this is Matt to show intro stats and I'll see you next time