 # Practice English Speaking&Listening with: Calculating the linear correlation coefficient and equation of regression line, using the TI-84

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Let's use the T I-84 to calculate the correlation coefficient and also to find the equation of the linear regression line.

Before we do this, we need to activate a feature on our calculator, and we're going to do that by going to the catalog. And if I look above the 0 key,

I'll see in teeny tiny little print, the word "catalog". To access it, I'll press the "2nd" key and then the "0" key. And, that's my catalog. This is just

an index of all of the functions on your calculator. So, I'll scroll down down down or I know that I'm heading to the entries that begin with the the letter

D, so maybe I'll just press the key that corresponds to the letter "D", and that'll take me to the first entry that starts with the letter "D". Then

I'll scroll down from here and I'm looking for an entry that says diagnostics on and there it is "diagnosticon", so I press the "enter" key

and then "enter" again, and it tells me "done". So this has activated the diagnostics

on the calculator. Once I've done this now, I don't have to do this again

until someone resets the memory on my calculator-- that sort of thing. So let's suppose that I had entered data

into a couple of lists. So, my y-values are in List 1, my x-values are in List 2.

To calculate the correlation coefficient, I press the"stat" key, then I toggle to the right

to "calc" and I choose choice #4, which is linear regression. And, when I do that, I have to tell it which lists to look at....

So, my data is in List 1, so "2nd 1", comma "list 2".

When I press "enter", I see the equation of the regression line as well as the correlation coefficient. So the last entry

here, the r-value, is the correlation coefficient. If I had not taken the time to turn on the diagnostics, then I would not see these last two lines of data.

So, if your screen happens to only have information for the line and

not the r-values here, then that's what's happened. Your diagnostics are off.

The correlation coefficient here is 0.8. The equation of the regression line is above that and it's in the form y=ax + b

And then "a" would be replaced with the value of 0.8. "b" would be replaced with the value of 4.5. So the regression line

would be y = 0.8x + 4.5

Now if on this set of data, I had also drawn a scatter plot and I had gone through the motions to do that, I might be looking like this

If I want to see the line get drawn across the data, what I do is press my "y=" key, and my cursor is waiting for me to enter the equation

Now, I can type it in, if I've written it in on my paper. I could type it in by hand. But a slicker way to get the equation here is to press your

"vars" key and then choose #5, which is statistics.

And then toggle to the right to "equation". Then choice #1 is "regression equation". What your calculator will do is it will

pick up the very last regression equation it generated and pop it into this level

at y1. Now when I hit my "graph" key, I'll see the scatter plot but I also see

the line come across the screen.

The Description of Calculating the linear correlation coefficient and equation of regression line, using the TI-84

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