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From |
"Carlo Lazzaro" <carlo.lazzaro@tin.it> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: R: Re: choice of ANOVA for an ecological experiment |

Date |
Mon, 31 Jan 2011 19:17:41 +0100 |

Dear Jacob, I am not an expert in this field. For more details on split plot (and alternative designs), a good reference for your research is Doncaster CP, Davey AJH. Analysis of Variance and Covariance. How to choose and construct models for the life sciences. Cambridge: 2007. This textbook devotes an entire 5th chapter to split-plot designs (pages 141-178) and a worked example of split-plot model is detailed at pages 51-57. Sorry I cannot be more helpful. Kind Regards, Carlo -----Messaggio originale----- Da: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] Per conto di Jacob Felson Inviato: lunedì 31 gennaio 2011 18.28 A: statalist@hsphsun2.harvard.edu Oggetto: st: Re: choice of ANOVA for an ecological experiment Carlo, Good question. I've also done a MANOVA, yes. For the MANOVA as well, I'm wondering about the appropriate way to analyze the data -- split plot or something else. Jacob Felson On Sun, Jan 30, 2011 at 3:00 PM, Jacob Felson <felsonj@gmail.com> wrote: > Hello, > > I am wondering whether anyone might be able to advise me about the > best choice of ANOVA to analyze the results of an ecological > experiment. In each of eight ponds, a certain number of various > species were put into enclosures that were randomly assigned to a set > of four predator conditions. The four randomly assigned predator > conditions were: no predators, 8 predators, 16 predators, and 24 > predators. Each predator condition was assigned to 3 replicates. So > the total number of enclosures was: 8 ponds x 4 predator conditions x > 3 replicates = 96. The outcome variables include the number of > individuals remaining, the weight of the individuals remaining, and > the size of the individuals remaining. > > This experiment appears to follow a split-plot design. Is this > correct? That is, the error of the pond effect is distinct from the > error of the predator condition effect. The sum of squared error for > the pond would be equal to the sum of squares for the predator > condition. The sum of squared error for the predator condition would > be equal to the residual sum of squares. > > The predator condition variable is called density, and the outcome > variable is number of survivors. If all of this is accurate, then I'm > guessing that a simple model might be: > > anova survivors pond / density | pond / > > > Is this correct? One further issue is that the ponds are fixed, not > random. Unlike the textbook split-plot design, a whole-plot has not > been randomly assigned to ponds. Instead, there are simply 8 ponds, > within each of which individuals were collected and placed in > enclosures with varying predator conditions. > > > I would very much appreciate help on this issue! > > > Sincerely, > Jacob Felson > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Re: choice of ANOVA for an ecological experiment***From:*Jacob Felson <felsonj@gmail.com>

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