The sleeper effect: Artifact or phenomenon—A brief comment on Bell et al. (2013)

OBJECTIVE: Bell, Marcus, and Goodlad (2013) recently conducted a meta-analysis of randomized controlled additive trials and found that adding an additional component to an existing treatment vis-à-vis the existing treatment produced larger effect sizes on targeted outcomes at 6-months follow-up than at termination, an effect they labeled as a sleeper effect. One of the limitations with Bell et al.'s detection of the sleeper effect was that they did not conduct a statistical test of the size of the effect at follow-up versus termination. METHOD: To statistically test if the differences of effect sizes between the additive conditions and the control conditions at follow-up differed from those at termination, we used a restricted maximum-likelihood random-effect model with known variances to conduct a multilevel longitudinal meta-analysis (k = 30). RESULTS: Although the small effects at termination detected by Bell et al. were replicated (ds = 0.17-0.23), none of the analyses of growth from termination to follow-up produced statistically significant effects (ds < 0.08; p > .20), and when asymmetry was considered using trim-and-fill procedure or the studies after 2000 were analyzed, magnitude of the sleeper effect was negligible (d = 0.00). CONCLUSION: There is no empirical evidence to support the sleeper effect.

Addresses to young children, originally delivered in the Girl's Free School, Bell Lane

[Charlotte v. Rothschild] [[Elektronische Ressource]]

Die Volksschulen in England : (Nach der Lehrart Bell und Lancasters)

Niemeyer

Trapped in the Bell Jar: Mental Illness in College Students

This is a magazine article that explores the rising problem of mental health in college students, focusing on Connecticut. It explores the experiences of three college students dealing with depression and bipolar disorder, a family who lost a child to suicide, and the measures taken by colleges in Connecticut to curb the problem.

Der Berg Asamon : Bell. Jud. II 18, 11

Samuel Klein

Uromastix acanthinurus Bell. (Dornschwanz) in der Gefangenschaft

Anonym

Annie Bell, Hüftbild

Signatur des Originals: S 36/F08188