An important step when designing an empirical study is to justify the sample size that will be
collected. The key aim of a sample size justification for such studies is to explain how the …

Replication—an important, uncommon, and misunderstood practice—is gaining
appreciation in psychology. Achieving replicability is important for making research …

Psychologists must be able to test both for the presence of an effect and for the absence of
an effect. In addition to testing against zero, researchers can use the two one-sided tests …

Power analysis is an important tool to use when planning studies. This contribution aims to
remind read-ers what power analysis is, emphasize why it matters, and articulate when and …

Psychology advances knowledge by testing statistical hypotheses using empirical
observations and data. The expectation is that most statistically significant findings can be …

The sample size necessary to obtain a desired level of statistical power depends in part on
the population value of the effect size, which is, by definition, unknown. A common approach …

Pre-registration of studies before they are conducted has recently become more feasible for
researchers, and is encouraged by an increasing number of journals. However, because the …

When designing a study, the planned sample size is often based on power analyses. One
way to choose an effect size for power analyses is by relying on pilot data. A-priori power …

Unplanned optional stop** rules have been criticized for inflating Type I error rates under
the null hypothesis significance testing (NHST) paradigm. Despite these criticisms, this …

Psychological distance and abstraction both represent key variables of considerable interest
to researchers across cognitive, social, and developmental psychology. Moreover, largely …