Sentences with phrase «quadratic effects of time»

Model predictors included main effects and interactions of group with linear and quadratic effects of time (i.e., time and time squared, respectively), and the three - way interactions of 1 - year environmental factors × group × linear time and environmental factors × group × quadratic time.

Not exact matches

Individual growth curve models were developed for multilevel analysis and specifically designed for exploring longitudinal data on individual changes over time.23 Using this approach, we applied the MIXED procedure in SAS (SAS Institute) to account for the random effects of repeated measurements.24 To specify the correct model for our individual growth curves, we compared a series of MIXED models by evaluating the difference in deviance between nested models.23 Both fixed quadratic and cubic MIXED models fit our data well, but we selected the fixed quadratic MIXED model because the addition of a cubic time term was not statistically significant based on a log - likelihood ratio test.

But at the very moment when one considers joined piecewise linear approximations [fig 4], without giving the reasons why the system would change its characteristics at that very time, perhaps it is more sensible to look for mechanisms (or effects, if we are unsure of the mechanisms) that describe the changing rate of change (leading to quadratic description) or perhaps even other functional forms: periodic, logistic, cubic.

Because initial RR analyses revealed both quadratic and linear effects of time on treatment outcomes, we computed the log of the number of days since randomization for each assessment point and used these log values in all RR analyses.