You need to give the model formula that gave your output. There are two sources of variation (at least), within and between locations; though it looks as though your analysis may have tried to account for this (but if so, the terms are not laid out in a way that makes for ready interpretation. The design is such (two locations) that you do not have much of a check that effects are consistent over locations.
You need to check whether results really are similar for all cultivars and for all herbicides, so that it is legitimate to pool as happens in the overall analysis. If a herbicide:cultivar combination has little effect the variability may be large, while if it has a dramatic effect (kills everything!), there may be no variability to speak of. John Maindonald.
On 22 Feb 2005, at 10:06 PM, [EMAIL PROTECTED] wrote:
To: "'Bob Wheeler'" <[EMAIL PROTECTED]> Cc: r-help@stat.math.ethz.ch Subject: RE: [R] power.anova.test for interaction effects Reply-To: [EMAIL PROTECTED]
It's a rather complex model. A 37*4 factorial (37 cultivars[var]; 4
herbicide treatments[trt]) with three replications[rep] was carried out at
two locations[loc], with different randomizations within each rep at each
location.
Source DF Error Term MS Loc 1 Trt*rep(loc) 12314 Rep(loc) 4 Trt*rep(loc) 1230.5 Trt 3 Trt*rep(loc) 64.72 Trt*loc 3 Trt*rep(loc) 33.42 Trt*rep(loc) 12 Residual 76.78 Var 36 Var*trt*loc 93.91 Var*trt 108 Var*trt*loc 12.06 Var*trt*loc 144 Residual 43.09 Residual 575 NA 21.23
-----Original Message----- From: Bob Wheeler [mailto:[EMAIL PROTECTED] Sent: Monday, February 21, 2005 4:33 PM To: [EMAIL PROTECTED] Cc: r-help@stat.math.ethz.ch Subject: Re: [R] power.anova.test for interaction effects
Your F value is so low as to make me suspect your model. Where did the 144 denominator degrees of freedom come from?
John Maindonald email: [EMAIL PROTECTED] phone : +61 2 (6125)3473 fax : +61 2(6125)5549 Centre for Bioinformation Science, Room 1194, John Dedman Mathematical Sciences Building (Building 27) Australian National University, Canberra ACT 0200.
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