ERIC Number: EJ746317
Record Type: Journal
Publication Date: 2006-Sep
Confidence Intervals and Replication: Where Will the Next Mean Fall?
Cumming, Geoff; Maillardet, Robert
Psychological Methods, v11 n3 p217-227 Sep 2006
Confidence intervals (CIs) give information about replication, but many researchers have misconceptions about this information. One problem is that the percentage of future replication means captured by a particular CI varies markedly, depending on where in relation to the population mean that CI falls. The authors investigated the distribution of this percentage for ? known and unknown, for various sample sizes, and for robust CIs. The distribution has strong negative skew: Most 95% CIs will capture around 90% or more of replication means, but some will capture a much lower proportion. On average, a 95% CI will include just 83.4% of future replication means. The authors present figures designed to assist understanding of what CIs say about replication, and they also extend the discussion to explain how p values give information about replication.
Descriptors: Intervals, Misconceptions, Mathematical Concepts, Researchers, Investigations, Statistical Distributions, Sample Size, Robustness (Statistics)
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Publication Type: Journal Articles; Reports - Research
Education Level: N/A
Authoring Institution: N/A