00:01
All right, so we're looking at our bus data, and we want to get a regression equation, and i used a software to calculate it, a nova software to calculate it.
00:11
The coefficients for the intercept and the age, right here, in the slope, that is.
00:20
Because your age is your independent variable, so it's the slope times x.
00:24
That gives you maintenance cost.
00:26
So every year adds about $600 to the maintenance cost.
00:33
So there's that.
00:34
And we want to look at a sky diagram, and here it is.
00:38
Here's the age to cost sky diagram.
00:40
And it's positive, but you can see these little forks here.
00:44
If you remember from some of the other exercises with this text, these are different, there were some different brands for manufacturers that had different costs associated with them, some costs more than others.
00:56
So that's kind of an interesting thing to consider here.
01:01
Direct, it's going up.
01:03
It's pretty strong within these bands.
01:06
But overall it's kind of spreading out.
01:09
So for that, you'd probably want to look at these.
01:12
We'd want to go and to do further analysis, we'd want to look at what these groups were.
01:28
We want to get another equation, but this time we want to add an additional year to the maintenance, see what that does to the cost.
01:35
Let's the estimated maintenance cost for a 10 of us.
01:40
So it's funny about this.
01:42
We don't need to redo everything.
01:43
The if we add a year to the age so good one's made it insert one column here we do age plus one it's not going to change let me fix this because of age plus one be so it's not going to change the slope at all because if you look the slope is given by the r value the correlation coefficient over the standard deviation of y over the standard deviation of x so age is your x variable and if you just add to it doesn't change the variation it just shifts it that's all it does so it only really changes the x bar so let's go ahead and do this so we need the the means of these values of these range new ranges equals average of the h plus one and the average i say average because that's the formula i use and the r values stays the same as well the r is it means and you are here.
03:02
Maintenance cost and engage plus one.
03:09
7 .07.
03:10
Oh, sorry, we don't even need that.
03:15
Sorry about that.
03:16
Because the b stays the same.
03:17
Sorry, i jumped out of myself.
03:18
We don't need the r.
03:19
But you can see that.
03:21
It's useful to see it how this is kind of a strong relationship.
03:26
So the new constant equals the y bar, which we said is maintenance cost, minus the b value still the same times the x bar.
03:48
Wait, y bar, this is maintenance cost, minus the b value times the x bar.
04:03
Oh, that's right.
04:04
It shifts it down.
04:04
For some reason my brain was thinking it was float.
04:08
But no, it shifts that down, the constant down...