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Sample Size Planning for Longitudinal Models: Accuracy in Parameter Estimation for Polynomial Change Parameters
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Kelley, Ken; Rausch, Joseph R. – Psychological Methods, 2011
Longitudinal studies are necessary to examine individual change over time, with group status often being an important variable in explaining some individual differences in change. Although sample size planning for longitudinal studies has focused on statistical power, recent calls for effect sizes and their corresponding confidence intervals…
Descriptors: Intervals, Sample Size, Effect Size, Longitudinal Studies
On Confidence Intervals for Within-Subjects Designs
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Blouin, David C.; Riopelle, Arthur J. – Psychological Methods, 2005
Confidence intervals (CIs) for means are frequently advocated as alternatives to null hypothesis significance testing (NHST), for which a common theme in the debate is that conclusions from CIs and NHST should be mutually consistent. The authors examined a class of CIs for which the conclusions are said to be inconsistent with NHST in…
Descriptors: Intervals, Hypothesis Testing, Generalization, Statistical Significance
Conceptualizing and Testing Random Indirect Effects and Moderated Mediation in Multilevel Models: New Procedures and Recommendations
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Bauer, Daniel J.; Preacher, Kristopher J.; Gil, Karen M. – Psychological Methods, 2006
The authors propose new procedures for evaluating direct, indirect, and total effects in multilevel models when all relevant variables are measured at Level 1 and all effects are random. Formulas are provided for the mean and variance of the indirect and total effects and for the sampling variances of the average indirect and total effects.…
Descriptors: Testing, Models, Sampling, Context Effect