Operation Manual

Chapter 12: Statistics 207
Med-Med (ax+b)
Med-Med (median-median) fits the model equation y=ax+b to the data using the median-median line
(resistant line) technique, calculating the summary points x1, y1, x2, y2, x3, and y3. Med-Med displays
values for a (slope) and b (y-intercept).
Med-Med [Xlistname,Ylistname,freqlist,regequ]
LinReg (ax+b)
LinReg(ax+b) (linear regression) fits the model equation y=ax+b to the data using a least-squares fit. It
displays values for
a (slope) and b (y-intercept); when DiagnosticOn is set, it also displays values for r
2
and
r.
LinReg(ax+b) [Xlistname,Ylistname,freqlist,regequ]
QuadReg (ax
2
+bx+c)
QuadReg (quadratic regression) fits the second-degree polynomial y=ax
2
+bx+c to the data. It displays
values for
a, b, and c; when DiagnosticOn is set, it also displays a value for R
2
. For three data points, the
equation is a polynomial fit; for four or more, it is a polynomial regression. At least three data points
are required.
QuadReg [Xlistname,Ylistname,freqlist,regequ]
CubicReg—(ax
3
+bx
2
+cx+d)
CubicReg (cubic regression) fits the third-degree polynomial y=ax
3
+bx
2
+cx+d to the data. It displays
values for
a, b, c, and d; when DiagnosticOn is set, it also displays a value for R
2
. For four points, the
equation is a polynomial fit; for five or more, it is a polynomial regression. At least four points are
required.
CubicReg [Xlistname,Ylistname,freqlist,regequ]