00:02
We are given a data table of x and y coordinate pairs, and we're tasked with using a graphing utility to make a scatter plot, find the line of best fit, and also the r value.
00:16
This particular graph here was done using excel, and excel can automatically plot your data.
00:25
It can determine the r value if you use the correlation function.
00:29
And this guy's r value was negative 0 .7 -1495.
00:33
So it's an okay fit.
00:35
It's not fantastic.
00:36
And you can see from the data, there's clearly a downward trend of a line, but it's pretty widely spread.
00:43
Excel can also tell you the equation for the line of best fit, and that's part of formatting the trend line.
00:52
The second order of business was to determine the value of f of x at several x values.
00:59
And of course, first we had to decide if the data was appropriate for that.
01:03
So the first thing we're trying to find out is what is f of zero? and that is definitely a reasonable data point to try to find, given the data that we have.
01:15
It's inside the spread of x.
01:18
So when we look at the graph, we can see we expect the answer to be approximately three.
01:26
And of course, we would just by looking at the equation, right? f of 0 is going to end up just equaling the y intercept.
01:37
So it's negative 0 .4077 times 0 plus 2 .9457.
01:53
And when we calculate that out of the 0 .407 times 0 is 0, and we end up with the y intercept, probably obvious 9457.
02:05
All right, next data point.
02:08
The negative six, negative six is definitely also inside the data range, if you will.
02:18
And so if we look here just on the graph, we're going to expect the y value or the f of x, f of negative six, to be in the neighborhood of maybe five and a half.
02:31
That's our expected.
02:32
If we get too far off from that, then we'll assume a calculator fumbled.
02:36
So f of negative 6 equals negative 0 .477 times negative 6 plus 2 .9457.
02:55
And the calculator says 5 .3919.
03:04
Yeah, and that's awfully close to 5 .5 .5.
03:07
So we're going to say we probably did that right.
03:10
The next one, 12.
03:12
This one's debatable.
03:13
12 is on the outside of the x range, if you will.
03:19
But given how wide the x range is, i think it's reasonable to extrapolate to 12.
03:26
So that would, if we extended the line, that would take us right about here, which is approximately negative 2.
03:33
So let's go ahead and calculate that.
03:36
F of 12 would equal negative.
03:40
0 .4077 times negative 6.
03:46
Oops, it's negative 12, a positive 12...