this video is sort of a continuation from the last one okay so we have our our information we were comparing or seeing if there was a connection between sales and advertising dollars if you remember we got an R value of point eight nine and so that was up at y equals our value is 0.89 that's a strong positive connection which means we can use the linear regression equation to make some predictions and so that's the advantage I should put strong positive correlation because it is a positive value so I put that correlation sorry the regression line equation at the top of this that we calculated in the last video and we want to use it to make predictions so what I need you to be careful of is which one of these stands for X and which is y in this case the first set of numbers we put into our calculator were the sales values so those are our X values and the advertising are our Y values and the way that this equation is set up is it really is set up so that you can find out why if somebody gives you X you would plug that number into this equation where the X is and do this calculation and it will tell you what the Y is so the way our equation is set up we would be able to tell for instance how many advertising dollars will likely be needed for a certain amount of sales projections now generally speaking you don't want to stray too far from the numbers in your X column so I would not it would not be appropriate for me to use this prediction equation for something like two hundred and fifty four sales projections in the thousands that's too far away from the span of numbers that are included here so it's really only effective for the numbers right around these involved in this chart but let's go ahead and talk about that so let's do a prediction let's say I'm looking for sales projections for the following January of 125 so your book your book will say you know to be a purist you should not go outside this list but 125 is close enough that our projection equation will be relatively effective so I want to predict what's the y-value if I know that I have sales projections of 125 so I want to know in this case I'm trying to find y which is advertising dollars for a given X which in this case are sales so I want to know what what should I what advertising dollars should I expect to spend so that I get 125,000 in sales and so it's just a plug and chug an old-fashioned plug and chug is sometimes we say in algebra I'm sorry about that I'm trying to move this and it's all different pieces so go back to your equation in purple this time I have a number that I want to plug in for X so in your calculator you're going to do point O five seven times my x value which is 125 and then minus 0.34 for you do that all in one step in your calculator and you get six point seven eight so that tells you you need to plan on if you round to the nearest tenth about six point eight thousand in advertising dollars to be able to project that amount of sales