# 19-21 Modern advances - Researcher and statistician error...

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1 Researcher and statistician error ~8% of biomedical papers have substantial statistical flaws 2 Publication bias Papers are more likely to be published if P <0.05 This causes a bias in the science reported in the literature. Computer-intensive methods ! Hypothesis testing: ! Simulation ! Randomization ! Confidence intervals ! Bootstrap Simulation ! Simulates the sampling process on a computer many times: generates the null distribution from estimates done on the simulated data ! Computer assumes the null hypothesis is true

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ratios Social spiders live in groups Example: Social spider sex ratios ! Groups are mostly females ! Hypothesis: Groups have just enough males to allow reproduction ! Test: Whether distribution of number of males is as predicted by chance ! Problem: Groups are of many different sizes ! Binomial distribution therefore doesn’t apply Simulation: ! For each group, the number of spiders is known. The overall proportion of males, p m , is known. ! For each group, the computer draws the real number of spiders, and each has p m probability of being male. ! This is done for all groups, and the variance in proportion of males is calculated. ! This is repeated a large number of times. 0.5 1. 1.5 2. 2.5 3. 3.5 200 400 600 800 1000 Variance in proportion of males (Pseudo-values) Frequency Actual Observed Value (0.44) The observed value (0.44), or something more extreme, is observed in only 4.9% of the simulations. Therefore
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## This note was uploaded on 04/16/2010 for the course MATHEMATIC 1231 taught by Professor Driscoll during the Spring '10 term at Clayton College of Natural Health.

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19-21 Modern advances - Researcher and statistician error...

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