I don't see a question. But here are a couple of comments. On 14 Sep 2003 18:47:21 -0700, [EMAIL PROTECTED] (cbsteh) wrote:
> I am interested to test the effects of 4 rates of organic matter (OM) > on soil compaction at 2 soil depths over 6 time periods (every 3 > months for 2 years). Including 0, I count 9 time periods. > I will divide an experimental field into 12 sections where every 3 > sections (selected randomly) will receive the same OM rate. This means > for every OM rate, there will be 3 replicates (i.e., 3 reps x 4 OM > rates = 12 sections/plots). The soil compaction at 2 soil depths, in > every section, will be measured repeatedly for 6 times. > > My suggested exp. design is a three-factor 4x2x6 factorial design with > repeated measures on the last 2 factors (soil depth and time). In > other words, this is a one between- (OM rates) and two within-subjects > (soil depths and time) design. > > The reason I am treating the soil depth factor as a within-subject > factor is that any effects on soil properties in two soil depths tend > to be correlated. This means if OM affects soil compaction in one soil > depth in one way, it will also tend to affect the other soil depth in > the same way (albeit in a smaller degree). This is because soil > properties from two soil depths have similar (but not equivalent) > properties, so they both tend to be correlated. > > Please advise. Thank you for the time and trouble. Do you expect a trend that increases (say) with depth? - a trend that increases with time? Is there literature that suggests what you should expect? A test of hypothesis that has one or two degrees of freedom is going to be more powerful and meaningful than an overall test across multiple periods in "two years". How big are the plots? (A "field" sounds large enough, but that could vary by a lot.) Do you take multiple core-samples to make up one assay of density? Is an ordinary crop (with roots) being grown, for those two years? - If this is not pragmatically aimed at some crop, then what is the focus of study? -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html "Taxes are the price we pay for civilization." . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
