> - Does "internal consistency" as the measure of reliability > make much sense for a time series? How tightly linked are > the measures? If there is a high lagged correlation, then > any 'internal consistency' is foolish to think about. Before > you worry about that ratio, in fact, I think the nature of the > time-series needs to be worked out. > > Is there an external criterion for this quotient, or is it > intended to predict itself-in-the-future, and nothing more? > > Maybe a real-life example would impress me otherwise, > but what comes to mind here, in the abstract, is that > a) test-retest reliability would be more convincing; and > b) even more than the usual cross-sectional report, > your conclusions will be heavily tied to the character > of the 'sample'; however well the quotient works, that > depends on various variances remaining similar.
Thank you for your answers and comments on my problem. I'd like to go into detail. The 18 Items are measurements of concentration performance: item1=concentration performance in the 1st testminute ... item18= concentration performance in the 18th testminute. The quotient [Mean(item7, ... item 18)/Mean(item1, ... item6)] is a simple measure of the enduring concentration performance of a person. I'd like to know a way to calculate the reliability (�true variance") of this measure. I measured N=102 subjects just for once, so I can�t calculate a retest-reliability. The lagged autocorrelation of the 18 occassions (18 testminutes): lag0 1 lag1 0,95 lag2 0,89 lag3 0,76 lag4 0,58 lag5 0,31 Hope this helps you to give me further answers. Many thanks in advance Frank Goldhammer . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
