Median Line of Regression (1 Viewer)

[Paj20]

To work out the gradient... you take two points that the line goes through and work out rise over run... but what if the line dosent go through any of the points on the graph? How is the gradient worked out then??


Thanks.

 

[PC]

If you're doing a median line of regression then remember you have to split the points into three sections. You then have to find a median point for each of the three sections.

Then you draw a line through the first and third median points. Finally, move this line vertically one-third of the way towards the second point.

Since the actual line of regression will be parallel to that first line, it will have the same gradient as that first line. Since that first line goes through the first and third median points, you can get the gradient from them - every time.

 

[Paj20]

If you're doing a median line of regression then remember you have to split the points into three sections. You then have to find a median point for each of the three sections.

Then you draw a line through the first and third median points. Finally, move this line vertically one-third of the way towards the second point.

Since the actual line of regression will be parallel to that first line, it will have the same gradient as that first line. Since that first line goes through the first and third median points, you can get the gradient from them - every time.

ohh so you can use the points after you moved it. kk thanks

 

[Paj20]

The rise over run is 6/6... and the book says the gradient is -1?

 

[PC]

What's your question?

Remember that you need to keep the co-ordinates in order.

For example, if the first median point is (25,45) and the third median point is (52,18) then:

Gradient = Rise/Run
= (y2 – y1)/(x2 – x1)
= (18 – 25)/(52 – 25)
= –27/27
= –1

 

[Paj20]

What's your question?

Remember that you need to keep the co-ordinates in order.

For example, if the first median point is (25,45) and the third median point is (52,18) then:

Gradient = Rise/Run
= (y2 – y1)/(x2 – x1)
= (18 – 25)/(52 – 25)
= –27/27
= –1

so the line is negative... sloping to the left.. so that means its rise is negative 6? and its run is 6.

so -6/6 equals -1 dosent it not 0 gradient?

 

[PC]

If the line looks like / then it will have a positive gradient.
If the line looks like \ then it will have a negative gradient.

The best way to do this is always work left to right. The run is how far you go across. Because you're going left to right, the run is always positive. Then work out the rise. If you have to go down to get back to the line then the gradient is negative. If you have to go up to get back to the line then the gradient is positive.