An Introduction to the Bootstrap

Efron, Bradley; Tibshrani, R.

doi:10.1007/978-1-4899-4541-9

Cited by 21,203 publications

(14,962 citation statements)

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“…Appendix A Notes on the Bootstrap Method Efron and Tibshirani (1993) described the bootstrap as "a computer-based method for assigning measures of accuracy to statistical estimates" (p. 10). The usual measure of accuracy for statistical quantities such as means, regression coefficients, and correlations is the standard error.…”

Section: Concluding Commentsmentioning

confidence: 99%

Mediation in experimental and nonexperimental studies: New procedures and recommendations.

Shrout¹,

Bolger²

2002

Psychological Methods

9,301

127

7,247

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Mediation is said to occur when a causal effect of some variable X on an outcome Y is explained by some intervening variable M. The authors recommend that with small to moderate samples, bootstrap methods (B. Efron & R. Tibshirani, 1993) be used to assess mediation. Bootstrap tests are powerful because they detect that the sampling distribution of the mediated effect is skewed away from 0. They argue that R. M. Baron and D. A. Kenny's (1986) recommendation of first testing the X → Y association for statistical significance should not be a requirement when there is a priori belief that the effect size is small or suppression is a possibility. Empirical examples and computer setups for bootstrap analyses are provided.

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Section: Concluding Commentsmentioning

confidence: 99%

Mediation in experimental and nonexperimental studies: New procedures and recommendations.

Shrout¹,

Bolger²

2002

Psychological Methods

9,301

127

7,247

View full text Add to dashboard Cite

show abstract

“…Our sample further includes both middle and high income countries, as classified by the World Bank 40 . To verify the robustness of our results, we calculated gender-unbiased estimates for activity inequality and obesity prevalence for each country by reweighting males and females in our sample to exactly match World Bank estimates 41 using a bootstrap 42 with 500 replications. In addition, we computed activity inequality separately for males and females in each country and then correlated the activity inequality for each gender with obesity prevalance for that gender.…”

Section: Methodsmentioning

confidence: 99%

Large-scale physical activity data reveal worldwide activity inequality

Althoff

Sosič

Hicks

et al. 2017

Nature

766

556

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Understanding the basic principles that govern physical activity is needed to curb the global pandemic of physical inactivity1–7 and the 5.3 million deaths per year associated with in-activity2. Our knowledge, however, remains limited owing to the lack of large-scale measurements of physical activity patterns across free-living populations worldwide1, 6. Here, we leverage the wide usage of smartphones with built-in accelerometry to measure physical activity at planetary scale. We study a dataset consisting of 68 million days of physical activity for 717,527 people, giving us a window into activity in 111 countries across the globe. We find inequality in how activity is distributed within countries and that this inequality is a better predictor of obesity prevalence in the population than average activity volume. Reduced activity in females contributes to a large portion of the observed activity inequality. Aspects of the built environment, such as the walkability of a city, were associated with less gender gap in activity and activity inequality. In more walkable cities, activity is greater throughout the day and throughout the week, across age, gender, and body mass index (BMI) groups, with the greatest increases in activity for females. Our findings have implications for global public health policy and urban planning and highlight the role of activity inequality and the built environment for improving physical activity and health.

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“…This spatial covariance pattern was characterized by relative increases in pallidothalamic, pontine, and cerebellar metabolism, associated with decreases in the premotor and posterior parietal areas. (The display represents voxels that contribute significantly to the network at P = 0.001 and that were showed to be reliable (P < 0.001) by bootstrap estimation (Efron and Tibshirani, 1994). Voxels with positive region weights (metabolic increases) are color coded from red to yellow; those with negative region weights (metabolic decreases) are color coded from blue to purple.)…”

Section: Statistical Proceduresmentioning

confidence: 99%

Abnormal Metabolic Network Activity in Parkinson'S Disease: Test—Retest Reproducibility

Tang

Spetsieris

et al. 2007

J Cereb Blood Flow Metab

281

385

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Parkinson's disease (PD) is associated with an abnormal pattern of regional brain function. The expression of this PD-related covariance pattern (PDRP) has been used to assess disease progression and the response to treatment. In this study, we validated the PDRP network as a measure of parkinsonism by prospectively computing its expression (PDRP scores) in 15 O-water (H 2 15 O) and 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET) scans from PD patients and healthy volunteers. The reliability of this measure was also assessed within subjects using a test-retest design in mildly affected and advanced PD patients scanned at baseline and during treatment with levodopa or deep brain stimulation (DBS). We found that PDRP expression was significantly elevated in PD patients (P < 0.001) relative to controls in a prospective analysis of brain scans obtained with either H 2 15 O or FDG PET. A significant correlation (R 2 = 0.61; P < 0.001) was evident between PDRP scores computed from H 2 15 O and FDG images in PD subjects scanned with both tracers. Test-retest reproducibility was very high (intraclass correlation coefficient (ICC) > 0.92) for PDRP scores measured both within PET session and between sessions separated by up to 2 months. This high reproducibility was observed in both early stage and advanced PD patients scanned at baseline and during treatment. The within-subject variability of this measure was less than 10% for both unmedicated and treated conditions. These findings suggest that the PDRP network is a reproducible and stable descriptor of regional functional abnormalities in parkinsonism. The quantification of PDRP expression in PD patients can serve as a potential biomarker in PET intervention studies for this disorder.

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An Introduction to the Bootstrap

Cited by 21,203 publications

References 0 publications

Mediation in experimental and nonexperimental studies: New procedures and recommendations.

Mediation in experimental and nonexperimental studies: New procedures and recommendations.

Large-scale physical activity data reveal worldwide activity inequality

Abnormal Metabolic Network Activity in Parkinson'S Disease: Test—Retest Reproducibility

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