|
|
|
||
|
Scatter Diagram
Description :
When to Use: • When you have paired numerical data. • When trying to identify potential root causes of problems. • After brainstorming causes and effects using a fishbone diagram, to determine objectively whether a particular cause and effect are related. • When determining whether two effects that appear to be related both occur with the same cause.
1. Collect pairs of data where a 2. Draw a graph with the independent variable on the horizontal axis and the dependent variable on the vertical axis. For each pair of data, put a dot or a symbol where the x-axis value intersects the y-axis value. (If two dots fall together, put them side by side, touching, so that you can see both.) 3. Look at the pattern of points to see if a relationship is obvious. If the data clearly form a line or a curve, you may stop. The variables are correlated. You may wish to use regression or correlation analysis now. Otherwise, complete steps 4 through 7. 4. Divide points on the graph into four quadrants. If there are X points on the graph, 5. Count X/2 points from top to bottom and draw a horizontal line. 6. Count X/2 points from left to right and draw a vertical line. 7. If number of points is odd, draw the line through the middle point. 8. Count the points in each quadrant. Do not count points on a line. 9. Add the diagonally opposite quadrants. Find the smaller sum and the total of points in all quadrants.
11. B = points in upper right + points in lower left 12. Q = the smaller of A and B 13. N = A + B 14. Look up the limit for N on the trend test table. 15. If Q is less than the limit, the two variables are related. 16. If Q is greater than or equal to the limit, the pattern could have occurred from random chance.
|
| ||
|
Add Our RSS Feed
|
|||
|
|
|||
|
| |||