The usual terminology uses the number of "ways" to mean the number of
factors (categorical
or classification variables, with more than one degree of freedom per
factor).
The term covariate is used for continuous variables, with exactly one df.

On Wed, Jul 4, 2012 at 9:20 AM, syrvn <mentor_@gmx.net> wrote:

> Hi!
>
> as my subject says I am struggling with the different of a two-way ANOVA
> and
> a (two-way) ANCOVA.
>
> I found the following examples from this webpage:
>
> http://www.statmethods.net/stats/anova.html
>
> # One Way Anova (Completely Randomized Design)
> fit <- aov(y ~ A, data=mydataframe)
>
> # Randomized Block Design (B is the blocking factor)
> fit <- aov(y ~ A + B, data=mydataframe)
>
> # Two Way Factorial Design
> fit <- aov(y ~ A + B + A:B, data=mydataframe)
> fit <- aov(y ~ A*B, data=mydataframe) # same thing
>
> # Analysis of Covariance
> fit <- aov(y ~ A + x, data=mydataframe)
>
> I) The 1. example is pretty clear. A simple on way ANOVA.
>
> II) Is it correct to say that example 2. (which is called a Randomized
> Block
> Design) is a two way ANOVA?
>
> III) Example 3 is like example 2. (in case I was right in II) )  a two way
> ANOVA but including an interaction term. That's why
> they call it here a Factorial Design.
>
> So far so good.
>
> IV) For me, the ANCOVA (last example) looks like a two-way ANOVA. So in
> what
> way is the variable "x" different to variable "B" so that it is called an
> ANCOVA and not an ANOVA??? I presume that from the type of data R knows
> whether to perform an ANCOVA or an ANOVA.
>
> V) Is it right to say that the ANCOVA example is a two-way ANCOVA? Or can a
> one-way ANCOVA actually exists?
>
> You see I am a bit confused especially how R distinguishes between the
> ANCOVA and the two-way ANOVA?
>
> I hope to find some useful answers here.
>
> Cheers!
>
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/Difference-between-two-way-ANOVA-and-two-way-ANCOVA-tp4635403.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

	[[alternative HTML version deleted]]

