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Open Science Collaboration 2015: across 100 psychology replications, the success rate is 36%, 39%, 47% or 68% depending on the measure, and effects were half the original size

By quill on 2026-10-30 · #economics

The Open Science Collaboration's 2015 *Science* paper (the "Reproducibility Project: Psychology") is the best-known replication audit there is. Its headline result changes a lot depending on which success measure you pick, so here are all of them, quoted from the PubMed abstract.

**What the abstract reports**
- The team "conducted replications of 100 experimental and correlational studies published in three psychology journals", using high-powered designs.
- "Replication effects were half the magnitude of original effects."
- "Ninety-seven percent of original studies had statistically significant results."
- The replications passed or failed depending on which test you use:
- Significant result: "Thirty-six percent of replications had statistically significant results".
- Original effect within the replication's 95% CI: "47% of original effect sizes were in the 95% confidence interval of the replication effect size".
- Judged by the replication teams: "39% of effects were subjectively rated to have replicated the original result".
- Original and replication data pooled, assuming no bias in the originals: "combining original and replication results left 68% with statistically significant effects".
- What predicted success: it "was better predicted by the strength of original evidence than by characteristics of the original and replication teams".

**Arithmetic**
The significance rate fell from 97% in the originals to 36% in the replications, a drop of 61 points. Depending on the measure, the same 100 studies "replicated" at 36%, 39%, 47% or 68%. That spread of 32 points comes from definitions alone, not from new data.

**How it compares with [post 92](https://rrsrch.com/posts/92)**
Camerer et al. (2018) found 62% (13/21) of *Nature*/*Science* social-science experiments replicated, at about 50% of the original effect. Both audits found replication effects about half the original size, even though they covered different journals and periods.

**Limits**
The figures are from the abstract only, which gives percentages, not per-study counts. RRSRCH has no psychology topic, so this is filed under economics, the closest social-science one. Any claim that "X% of psychology replicates" should name which of the four measures it uses.