I would think that to look at just the overall distribution of these three time-series (I'm assuming your 3 methods of measurement yield 3 different time-series right?) tells you very little about their respective behavior in time; also, the distribution you estimate (histogram) is only a sample, and for nonstationary time-series one would expect that the distribution isn't very representative of the population (i.e., the underlying process is continually changing somehow). So summary statistics might be a first-step, but I would follow up with an ARIMA approach to modeling these three series. Examine their power-spectra as well. Follow that up with something like a PCA to see if they are somehow related in terms of variance components.
----- Original Message ----- From: "Euh" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, March 04, 2004 10:28 AM Subject: [edstat] How to compare trends ? > Hi all, > > I'm following the time course of a certain variable by using three > independent measurement techniques (for which I can estimate the > variance associated with the measurment) > > I can't really assume any function to describ the evolution of the > variable over time (linear, quadratic, etc). Is there a way to compare > the results and assess if all the methods give similar results ? > > ANOVA analysis at each time ? > > An example would be: > > Method 1 Method 2 Method 3 > mean stdev mean stdev mean stdev > t1 24.6 6.4 31.0 13.8 15.5 5.7 > t2 123.5 87.6 155.2 71.5 62.3 20.0 > t3 174.0 33.8 142.7 46.4 75.8 18.9 > t4 210.6 91.2 113.6 26.8 101.9 45.1 > t5 396.4 25.4 263.9 16.5 209.3 11.7 > t6 303.7 66.7 271.9 156.6 216.9 172.1 > t7 153.6 93.4 261.0 225.6 76.0 41.7 > t8 250.9 140.7 289.5 122.7 93.7 28.1 > . > . > ================================================================= > Instructions for joining and leaving this list, remarks about the > problem of INAPPROPRIATE MESSAGES, and archives are available at: > . http://jse.stat.ncsu.edu/ . > ================================================================= > . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
