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Subclinical delusional ideation and appreciation of sample size and heterogeneity in statistical judgment
Author(s) -
Galbraith Niall D.,
Manktelow Ken I.,
Morris Neil G.
Publication year - 2010
Publication title -
british journal of psychology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.536
H-Index - 92
eISSN - 2044-8295
pISSN - 0007-1269
DOI - 10.1348/000712609x479384
Subject(s) - psychology , subclinical infection , ideation , sample (material) , sample size determination , schizotypy , cognitive psychology , social psychology , clinical psychology , statistics , cognitive science , medicine , personality , chemistry , mathematics , chromatography
Previous studies demonstrate that people high in delusional ideation exhibit a data‐gathering bias on inductive reasoning tasks. The current study set out to investigate the factors that may underpin such a bias by examining healthy individuals, classified as either high or low scorers on the Peters et al. Delusions Inventory (PDI). More specifically, whether high PDI scorers have a relatively poor appreciation of sample size and heterogeneity when making statistical judgments. In Expt 1, high PDI scorers made higher probability estimates when generalizing from a sample of 1 with regard to the heterogeneous human property of obesity. In Expt 2, this effect was replicated and was also observed in relation to the heterogeneous property of aggression. The findings suggest that delusion‐prone individuals are less appreciative of the importance of sample size when making statistical judgments about heterogeneous properties; this may underpin the data gathering bias observed in previous studies. There was some support for the hypothesis that threatening material would exacerbate high PDI scorers' indifference to sample size.