THE STATISTICAL-ANALYSIS OF TIDAL RHYTHMS - TESTS OF THE RELATIVE EFFECTIVENESS OF 5 METHODS USING MODEL SIMULATIONS AND ACTUAL DATA

Endogenous rhythms in intertidal organisms are often very complex and imprecise. Thus, confusing results are sometimes obtained when applyin g various interpretive analytical techniques. In an attempt to resolve this problem, ten different models representing typical organismic ti dal-rhythm displays were created and examined with five different infe rential statistical techniques. The exercise was designed to test the relative effectiveness of these techniques in detecting the presence o f known cycles in the models, and estimating their period lengths. The same comparison was then repeated on sets of animal-derived data. All of the five methods had their merits, but, depending on the model bei ng examined, the results from the various methods were not identical. Three of the techniques produce harmonics, making data that contain mu ltiple periods especially difficult to decipher. Often both tidal and circadian periods are displayed by shore dwellers; all five methods we re able to find these two periods. But when the difference in circa pe riod length was close, only one technique (array analysis) could make a distinction. This technique was also the only one able to handle dat a in which the period was not constant. Interestingly, this simplest o f methods is probably the best all-round method of discovery. Many mor e subtle, but important, differences were also noted, and it is recomm ended that more than one method always be used to ensure accuracy.