Understanding Power and Rules of Thumb for Determining Sample Sizes
Bibliographic record
Abstract
This article addresses the definition of power and its relationship to Type I and Type II errors.We discuss the relationship of sample size and power.Finally, we offer statistical rules of thumb guiding the selection of sample sizes large enough for sufficient power to detecting differences, associations, chi-square, and factor analyses.As researchers, it is disheartening to pour time and intellectual energy into a research project, analyze the data, and find that the elusive .05significance level was not met.If the null hypothesis is genuinely true, then the findings are robust.But, what if the null hypothesis is false and the results failed to detect the difference at a high enough level?It is a missed opportunity.Power refers to the probability of rejecting a false null hypothesis.Attending to power during the design phase protect both researchers and respondents.In recent years, some Institutional Review Boards for the protection of human respondents have rejected or altered protocols due to design concerns (Resnick, 2006).They argue that an "underpowered" study may not yield useful results and consequently unnecessarily put respondents at risk.Overall, researchers can and should attend to power.This article defines power in accessible ways, provides guidelines for increasing power, and finally offers "rules-of-thumb" for numbers of respondents needed for common statistical procedures.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.269 | 0.723 |
| Meta-epidemiology (narrow) | 0.004 | 0.003 |
| Meta-epidemiology (broad) | 0.006 | 0.003 |
| Bibliometrics | 0.012 | 0.008 |
| Science and technology studies | 0.003 | 0.017 |
| Scholarly communication | 0.013 | 0.020 |
| Open science | 0.009 | 0.009 |
| Research integrity | 0.008 | 0.016 |
| Insufficient payload (model declined to judge) | 0.005 | 0.003 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; the direct Gemma label and the distilled Codex classifier agree on what is shown here.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".