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[23] Ceiling Effects and Replications

Posted on June 4, 2014February 11, 2020 by Uri Simonsohn

A recent failure to replicate led to an attention-grabbing debate in psychology. As you may expect from university professors, some of it involved data.  As you may not expect from university professors, much of it involved saying mean things that would get a child sent to the principal's office (.pdf). The hostility in the debate has obscured an interesting…

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[22] You know what's on our shopping list

Posted on May 22, 2014February 16, 2020 by Leif Nelson

As part of an ongoing project with Minah Jung, a nearly perfect doctoral student, we asked  people to estimate the percentage of people who bought some common items in their last trip to the supermarket. For each of 18 items, we simply asked people (N = 397) to report whether they had bought it on…

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[21] Fake-Data Colada: Excessive Linearity

Posted on May 8, 2014February 11, 2020 by Leif and Uri

Recently, a psychology paper (.html) was flagged as possibly fraudulent based on statistical analyses (.pdf). The author defended his paper (.html), but the university committee investigating misconduct concluded it had occurred (.pdf). In this post we present new and more intuitive versions of the analyses that flagged the paper as possibly fraudulent. We then rule…

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[20] We cannot afford to study effect size in the lab

Posted on May 1, 2014January 30, 2020 by Uri Simonsohn

Methods people often say  – in textbooks, task forces, papers, editorials, over coffee, in their sleep – that we should focus more on estimating effect sizes rather than testing for significance. I am kind of a methods person, and I am kind of going to say the opposite. Only kind of the opposite because it…

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[19] Fake Data: Mendel vs. Stapel

Posted on April 14, 2014February 11, 2020 by Uri Simonsohn

Diederik Stapel, Dirk Smeesters, and Lawrence Sanna published psychology papers with fake data. They each faked in their own idiosyncratic way, nevertheless, their data do share something in common. Real data are noisy. Theirs aren't. Gregor Mendel's data also lack noise (yes, famous peas-experimenter Mendel). Moreover, in a mathematical sense, his data are just as…

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[18] MTurk vs. The Lab: Either Way We Need Big Samples

Posted on April 4, 2014February 12, 2020 by Joe Simmons

Back in May 2012, we were interested in the question of how many participants a typical between-subjects psychology study needs to have an 80% chance to detect a true effect. To answer this, you need to know the effect size for a typical study, which you can’t know from examining the published literature because it…

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[17] No-way Interactions

Posted on March 12, 2014February 11, 2020 by Uri Simonsohn

This post shares a shocking and counterintuitive fact about studies looking at interactions where effects are predicted to get smaller (attenuated interactions). I needed a working example and went with Fritz Strack et al.’s  (1988, .html) famous paper [933 Google cites], in which participants rated cartoons as funnier if they saw them while holding a…

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[15] Citing Prospect Theory

Posted on February 10, 2014February 12, 2020 by Uri Simonsohn

Kahneman and Tversky's (1979) Prospect Theory (.html), with its 9,206 citations, is the most cited article in Econometrica, the prestigious journal in which it appeared. In fact, it is more cited than any article published in any economics journal. [1] Let's break it down by year. To be clear, this figure shows that just in 2013, Prospect Theory got about…

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[13] Posterior-Hacking

Posted on January 13, 2014January 30, 2020 by Uri Simonsohn

Many believe that while p-hacking invalidates p-values, it does not invalidate Bayesian inference. Many are wrong. This blog post presents two examples from my new “Posterior-Hacking” (SSRN) paper showing  selective reporting invalidates Bayesian inference as much as it invalidates p-values. Example 1. Chronological Rejuvenation experiment In  “False-Positive Psychology" (SSRN), Joe, Leif and I run experiments to demonstrate how easy…

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[12] Preregistration: Not just for the Empiro-zealots

Posted on January 7, 2014January 23, 2019 by Leif Nelson

I recently joined a large group of academics in co-authoring a paper looking at how political science, economics, and psychology are working to increase transparency in scientific publications. Psychology is leading, by the way. Working on that paper (and the figure below) actually changed my mind about something. A couple of years ago, when Joe,…

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    © 2021, Uri Simonsohn, Leif Nelson, and Joseph Simmons. For permission to reprint individual blog posts on DataColada please contact us via email..