Category Size Bias in Probability Judgments (#195)

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How to Cite this Report

APA Style

Hannah Perfecto, Leif D. Nelson. Category Size Bias in Probability Judgments. (2014, June 17). Retrieved 16:10, August 17, 2017 from

MLA Style

"Category Size Bias in Probability Judgments" Hannah Perfecto, Leif D. Nelson. 17 Jun 2014 02:12 17 Aug 2017, 16:10 <>

MHRA Style

'Category Size Bias in Probability Judgments', Hannah Perfecto, Leif D. Nelson, , 17 June 2014 02:12 <> [accessed 17 August 2017]

Chicago Style

"Category Size Bias in Probability Judgments", Hannah Perfecto, Leif D. Nelson, , (accessed August 17, 2017)


Category Size Bias in Probability Judgments [Internet]. Hannah Perfecto, Leif D. Nelson; 2014 Jun 17, 02:12 [cited 2017 Aug 17]. Available from:

Reference to Original Report of Finding Isaac, M. S., & Brough, A. R. (in press, 2014). Judging a part by the size of its whole: The category size bias in probability judgments. Journal of Consumer Research.
Title Category Size Bias in Probability Judgments
If the original article contained multiple experiments, which one did you attempt to replicate? e.g., you might respond 'Study 1' or 'Experiment 4'. Study 3
Link to PDF of Original ReportView Article
Brief Statement of Original Result Study 3 showed outcomes from a large category (a consonant, T, coming up on a 26-sided alphabet die) were seen as more likely than outcomes from a small category (a vowel, A). This difference was largest when the category was made salient.
Type of Replication Attempted Highly Direct Replication
Result Type Successful Replication
Difference? Same Direction, .012
Number of Subjects 505
Number of Subjects in Original Study 175
Year in which Replication Attempt was Made 2014
Name of Investigators (Real Names Required) Hannah Perfecto, Leif D. Nelson
Detailed Description of Method/Results The authors generously provided their study materials in the paper, which we used for our replication. In analyzing the data, not all responses were in the correct format (i.e., a percentage) hence we coded these as follows: 1/26-->3.85, if x<1--> x*100, and, in one case, 38-->3.8.

We successfully replicated the interaction between category size (T/large vs. A/small) and category salience (high vs. medium vs. low), F(2, 499)=3.71, p<.03. Further analyses revealed a successful replication of their simple effect under high salience, such that the large-category outcome was predicted to be more likely (M=14.3%) than the small-category outcome (M=7.0%), t(162)=2.54, p<.02. We also successfully replicated their absence of a simple effect under low salience--t(158)=.64, p>.52--but failed to replicate their (non-crucial) simple effect under medium salience, t(162)=.03, p>.97. The full write-up is included as a PDF. Any parties interested in the raw data may contact H.P.

Figure 1 shows both the original paper's graph of the six conditions' means as well as our replication's. Figure 2 shows that our replication was an informative and successful one, based on sample and effect sizes (Simonsohn, 2013).
Any Known Methodological Differences
(between original and present study)?
Through subsequent correspondence, we learned that Isaac and Brough also showed participants an image of the die in question. This was not included in the description of their materials, so we did not include it in our replication. Additionally, Isaac & Brough provided participants with a blank line ending in a percentage sign to give their answer. Due to programming difficulties, we did not have this and instead told participants to reply in the form of a percentage. Deviations from this were coded according to the coding scheme described in the "Detailed Description of Methods/Results" section.
Email of Investigator
Name of individuals who
actually carried out the project
H.P created the survey and posted it online for participants. H.P. and L.D.N. analyzed the data.
Location of ProjectUC Berkeley (online)
Characteristics of Subjects
(subject pool, paid, etc.)
Adults tested through internet
Amazon Mechanical Turk, US only
Where did these subjects reside?United States
Was this a Class Project?No
Further Details of Results as pdf PDF

Additional Comments
Email of Original Investigator
Quantitive Information
I have complied with ethical standards for experimentation on human beings and, if necessary, have obtained appropriate permission from an Institutional Review Board or other oversight group.
TAG: Attention TAG: JDM TAG: Language TAG: Learning TAG: Memory TAG: Perception TAG: Performance TAG: Problem Solving TAG: Social Cognition TAG: Social Psychology TAG: Thinking

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