When trying to identify potential root causes of problems.When trying to determine whether the two variables are related, such as:.When your dependent variable may have multiple values for each value of your independent variable.This cause analysis tool is considered one of the seven basic quality tools. The better the correlation, the tighter the points will hug the line. If the variables are correlated, the points will fall along a line or curve. The scatter diagram graphs pairs of numerical data, with one variable on each axis, to look for a relationship between them. Extending that to a 6th order polynomial should be straightforward.Quality Glossary Definition: Scatter diagram The help file ( ) includes an example for a 3rd order polynomial. If this is something you will need to do frequently, I recommend that you become familiar with using the LINEST() function to perform polynomial regressions. If this is a one time or rare task, then it is probably easiest to simply hand enter the coefficients into the spreadsheet. In all of these scenarios, the main "difficulty" to your problem is that you have used the chart trendline feature to perform the regression, so you need to transfer the equations coefficients into the spreadsheet. Usually the easiest approach is to use Excel's built in Solver/Goal Seek utilities. For a 6th order polynomial, this is not possible algebraically, but one can easily use numerical algorithms to solve for x at a given z. For other values of x, simply put that value for x in and compute z.įrom your original post, I first thought you were looking to give the equation z, then find x. I will agree, you could be clearer about what exactly you want.Īs 6stringjazzer notes, to obtain the z value at x=0, simply put 0 in for x in the trendline and compute y (which is just the constant term in the polynomial).
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