Can someone please explain to me about the contrast statement?
For example, to test the linear/quadratic/cubic trend of a 4-level variable, the contrast statements will be
Linear -3 -1 1 3 Quad 1 -1 -1 1 Cubic -1 3 -3 1.
I just can't get my head around how it is -3 -1 1 3 for linear, 1 -1 -1 1 for quadratic and -1 3 -3 1 for cubic. I only understand they need to sum up to zero.
ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.