MBESS 5.0.1 (2026)

Maintenance release. Corrects the sampling-variance scaling in the polynomial change model sample size planner ss.aipe.pcm().

• ss.aipe.pcm(): the single-subject sampling variance of the change coefficient now includes the factor frequency^(2m) (where m is the order of the polynomial trend), matching Raudenbush and Liu (2001) and the companion power function ss.power.pcm(). Previously this factor was omitted, so for designs measured more than once per unit of time (frequency greater than 1) the planned sample size was too small and the resulting confidence interval was wider than requested. Results for frequency = 1 are unchanged, including the published Kelley and Rausch (2011) examples, which still return 278 and 316.
• ss.aipe.pcm(): corrected the constant for a cubic trend from 1/1000800 to the correct 1/100800 (that is, (3!)^2 / (6! 7!)). The earlier value, a transcription error with an extra digit, inflated the implied error variance for trend = "cubic" by a factor of about 9.93 and so overstated the planned sample size. Linear and quadratic trends were unaffected.
• ss.aipe.pcm(): in the assurance branch, the t critical value is now recomputed as the sample size iterates rather than reusing the value from the expected-width search. The numerical effect is small, but the previous code used a critical value carrying the wrong degrees of freedom.

MBESS 5.0.0 (2026)

Maintenance release. MBESS is mature, stable, and widely used, and it remains fully supported. Maintenance mode does not mean the package is finished or abandoned: MBESS will continue to be maintained so that it keeps working with current versions of R and its dependencies, and it will remain on CRAN. New methodological development now takes place in the successor package, DMAR (Design, Measurement, and Analysis in R), which is available on CRAN. MBESS and DMAR are designed to coexist; existing code that relies on MBESS will keep working, so there is no need to migrate.

• Documentation and references brought up to date. Citations that had previously appeared as “submitted”, “in press”, or “under review” now cite the published articles (for example, Kelley, 2008; Kelley & Lai, 2011; Lai & Kelley, 2012; Chattopadhyay & Kelley, 2016, 2017; Lachowicz, Preacher, & Kelley, 2018; Li, McLouth, & Delaney, 2020).
• Numerous spelling and typographical corrections throughout the help pages.
• ci.reliability(): fixed a misnamed variable that caused the lower/upper logit confidence limit swap to be skipped in an edge case.
• Internal calls into Suggested packages were brought up to their current, fully namespaced forms. ss.aipe.rmsea.sensitivity() now calls sem::sem() directly, so it no longer fails when the sem package is installed but not attached. ci.reliability() now uses lavaan::lavInspect() in place of the older lavaan::inspect(), with identical numerical results.
• Added an inst/CITATION file, this NEWS file, and an expanded README.
• Contributor acknowledgments now ship with the package (see the CONTRIBUTORS file in the installed package) rather than depending on an external web page.

MBESS 4.0.0 (2016)

Major release.

MBESS 3.0.0 (2010)

Major release. Versions 3.0.0 through 3.3.3 included Keke (Brian) Lai as coauthor and maintainer. Lai, Ken Kelley’s doctoral advisee at Indiana University and the University of Notre Dame, has since stepped away from package maintenance and development, but his contributions to individual functions remain and he is credited as their coauthor.

MBESS 2.0.0 (2008)

Major release.

MBESS 1.0.0 (2007)

Major release.

MBESS 0.0.1 (2006-05-06)

First public release.