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Full-Text Articles in Law

Power And Statistical Significance In Securities Fraud Litigation, Jill E. Fisch, Jonah B. Gelbach Jan 2021

Power And Statistical Significance In Securities Fraud Litigation, Jill E. Fisch, Jonah B. Gelbach

Faculty Scholarship at Penn Law

Event studies, a half-century-old approach to measuring the effect of events on stock prices, are now ubiquitous in securities fraud litigation. In determining whether the event study demonstrates a price effect, expert witnesses typically base their conclusion on whether the results are statistically significant at the 95% confidence level, a threshold that is drawn from the academic literature. As a positive matter, this represents a disconnect with legal standards of proof. As a normative matter, it may reduce enforcement of fraud claims because litigation event studies typically involve quite low statistical power even for large-scale frauds.

This paper, written for ...


A Data Set Of Bloodstain Patterns For Teaching And Research In Bloodstain Pattern Analysis: Gunshot Backspatters, Daniel Attinger, Yu Liu, Ricky Faflak, Yalin Rao, Bryce A. Struttman, Kris De Brabanter, Patrick M. Comiskey, Alex L. Yarin Nov 2018

A Data Set Of Bloodstain Patterns For Teaching And Research In Bloodstain Pattern Analysis: Gunshot Backspatters, Daniel Attinger, Yu Liu, Ricky Faflak, Yalin Rao, Bryce A. Struttman, Kris De Brabanter, Patrick M. Comiskey, Alex L. Yarin

Mechanical Engineering Publications

This is a data set of blood spatter patterns scanned at high resolution, generated in controlled experiments. The spatter patterns were generated with a rifle or a handgun, and different ammunitions. The resulting atomized blood droplets travelled opposite to the bullet direction, generating a gunshot backspatter on a poster board target sheet. Fresh blood with anticoagulants was used; its hematocrit and temperature were measured. Main parameters of the study were the bullet shape, size and speed, and the distance between the blood source and target sheet. Several other parameters were explored in a less systematic way. This new and original ...


Surprise Vs. Probability As A Metric For Proof, Edward K. Cheng, Matthew Ginther Jan 2018

Surprise Vs. Probability As A Metric For Proof, Edward K. Cheng, Matthew Ginther

Vanderbilt Law School Faculty Publications

In this Symposium issue celebrating his career, Professor Michael Risinger in Leveraging Surprise proposes using "the fundamental emotion of surprise" as a way of measuring belief for purposes of legal proof. More specifically, Professor Risinger argues that we should not conceive of the burden of proof in terms of probabilities such as 51%, 95%, or even "beyond a reasonable doubt." Rather, the legal system should reference the threshold using "words of estimative surprise" -asking jurors how surprised they would be if the fact in question were not true. Toward this goal (and being averse to cardinality), he suggests categories such ...


The Logic And Limits Of Event Studies In Securities Fraud Litigation, Jill E. Fisch, Jonah B. Gelbach, Jonathan Klick Jan 2018

The Logic And Limits Of Event Studies In Securities Fraud Litigation, Jill E. Fisch, Jonah B. Gelbach, Jonathan Klick

Faculty Scholarship at Penn Law

Event studies have become increasingly important in securities fraud litigation after the Supreme Court’s decision in Halliburton II. Litigants have used event study methodology, which empirically analyzes the relationship between the disclosure of corporate information and the issuer’s stock price, to provide evidence in the evaluation of key elements of federal securities fraud, including materiality, reliance, causation, and damages. As the use of event studies grows and they increasingly serve a gatekeeping function in determining whether litigation will proceed beyond a preliminary stage, it will be critical for courts to use them correctly.

This Article explores an array ...


Introduction: Symposium On “Forensics, Statistics, And Law”, Brandon L. Garrett Jan 2018

Introduction: Symposium On “Forensics, Statistics, And Law”, Brandon L. Garrett

Faculty Scholarship

No abstract provided.


Constitutionalism And Democracy Dataset, Version 1.0, Todd A. Eisenstadt, Carl Levan, Tofigh Maboudi May 2017

Constitutionalism And Democracy Dataset, Version 1.0, Todd A. Eisenstadt, Carl Levan, Tofigh Maboudi

Political Science: Faculty Publications and Other Works

The main objective of the CDD is to quantify the process of constitution-making since 1974. This is the first public release of any data on the process of constitution-making. This release includes data on 144 national constitutions promulgated in 119 countries from 1974 to 2014. The unit of analysis in the data is national constitutions. The data in this release includes only “new” constitutions and does not include suspended, re-installed, amended, or interim constitutions. In this release, only countries with a population larger than 500,000 are included. The authors intend to update the data by including all countries, expanding ...


Error Costs, Legal Standards Of Proof And Statistical Significance, Michelle Burtis, Jonah B. Gelbach, Bruce H. Kobayashi Apr 2017

Error Costs, Legal Standards Of Proof And Statistical Significance, Michelle Burtis, Jonah B. Gelbach, Bruce H. Kobayashi

Faculty Scholarship at Penn Law

The relationship between legal standards of proof and thresholds of statistical significance is a well-known and studied phenomena in the academic literature. Moreover, the distinction between the two has been recognized in law. For example, in Matrix v. Siracusano, the Court unanimously rejected the petitioner’s argument that the issue of materiality in a securities class action can be defined by the presence or absence of a statistically significant effect. However, in other contexts, thresholds based on fixed significance levels imported from academic settings continue to be used as a legal standard of proof. Our positive analysis demonstrates how a ...


A General Approach For Predicting The Behavior Of The Supreme Court Of The United States, Daniel Katz Apr 2017

A General Approach For Predicting The Behavior Of The Supreme Court Of The United States, Daniel Katz

All Faculty Scholarship

Building on developments in machine learning and prior work in the science of judicial prediction, we construct a model designed to predict the behavior of the Supreme Court of the United States in a generalized, out-of-sample context. To do so, we develop a time-evolving random forest classifier that leverages unique feature engineering to predict more than 240,000 justice votes and 28,000 cases outcomes over nearly two centuries (1816-2015). Using only data available prior to decision, our model outperforms null (baseline) models at both the justice and case level under both parametric and non-parametric tests. Over nearly two centuries ...


The Reduced Form Of Litigation Models And The Plaintiff's Win Rate, Jonah B. Gelbach Sep 2016

The Reduced Form Of Litigation Models And The Plaintiff's Win Rate, Jonah B. Gelbach

Faculty Scholarship at Penn Law

In this paper I introduce what I call the reduced form approach to studying the plaintiff's win rate in litigation selection models. A reduced form comprises a joint distribution of plaintiff's and defendant's beliefs concerning the probability that the plaintiff would win in the event a dispute were litigated; a conditional win rate function that tells us the actual probability of a plaintiff win in the event of litigation, given the parties' subjective beliefs; and a litigation rule that provides the probability that a case will be litigated given the two parties' beliefs. I show how models ...


Motorcycle Helmet Effectiveness In Reducing Head, Face And Brain Injuries By State And Helmet Law, Cody S. Olsen, Andrea M. Thomas, Michael Singleton, Anna M. Gaichas, Tracy J. Smith, Gary A. Smith, Justin Peng, Michael J. Bauer, Ming Qu, Denise Yeager, Timothy Kerns, Cynthia Burch, Lawrence J. Cook Mar 2016

Motorcycle Helmet Effectiveness In Reducing Head, Face And Brain Injuries By State And Helmet Law, Cody S. Olsen, Andrea M. Thomas, Michael Singleton, Anna M. Gaichas, Tracy J. Smith, Gary A. Smith, Justin Peng, Michael J. Bauer, Ming Qu, Denise Yeager, Timothy Kerns, Cynthia Burch, Lawrence J. Cook

Biostatistics Faculty Publications

Background: Despite evidence that motorcycle helmets reduce morbidity and mortality, helmet laws and rates of helmet use vary by state in the U.S.

Methods: We pooled data from eleven states: five with universal laws requiring all motorcyclists to wear a helmet, and six with partial laws requiring only a subset of motorcyclists to wear a helmet. Data were combined in the Crash Outcome Data Evaluation System's General Use Model and included motorcycle crash records probabilistically linked to emergency department and inpatient discharges for years 2005-2008. Medical outcomes were compared between partial and universal helmet law settings. We estimated ...


Data, Data, Data, Mary Whisner Jan 2016

Data, Data, Data, Mary Whisner

Librarians' Articles

The legal profession often requires extensive data for everything from simple statistical questions to large-scale empirical research projects. Ms. Whisner discusses some of her favorite sources for finding and evaluating statistics.


Privacy And Accountability In Black-Box Medicine, Roger Allan Ford, W. Nicholson Price Ii Jan 2016

Privacy And Accountability In Black-Box Medicine, Roger Allan Ford, W. Nicholson Price Ii

Law Faculty Scholarship

Black-box medicine—the use of big data and sophisticated machine learning techniques for health-care applications—could be the future of personalized medicine. Black-box medicine promises to make it easier to diagnose rare diseases and conditions, identify the most promising treatments, and allocate scarce resources among different patients. But to succeed, it must overcome two separate, but related, problems: patient privacy and algorithmic accountability. Privacy is a problem because researchers need access to huge amounts of patient health information to generate useful medical predictions. And accountability is a problem because black-box algorithms must be verified by outsiders to ensure they are ...


Is The Time Allocated To Review Patent Applications Inducing Examiners To Grant Invalid Patents?: Evidence From Micro-Level Application Data, Michael D. Frakes, Melissa F. Wasserman Jan 2016

Is The Time Allocated To Review Patent Applications Inducing Examiners To Grant Invalid Patents?: Evidence From Micro-Level Application Data, Michael D. Frakes, Melissa F. Wasserman

Faculty Scholarship

We explore how examiner behavior is altered by the time allocated for reviewing patent applications. Insufficient examination time may hamper examiner search and rejection efforts, leaving examiners more inclined to grant invalid applications. To test this prediction, we use application-level data to trace the behavior of individual examiners over the course of a series of promotions that carry with them reductions in examination-time allocations. We find evidence demonstrating that such promotions are associated with reductions in examination scrutiny and increases in granting tendencies, as well as evidence that those additional patents being issued on the margin are of below-average quality.


A Socio-Demographic Analysis Of Responses To Terrorism, Gabriel Rubin, Christopher Salvatore May 2015

A Socio-Demographic Analysis Of Responses To Terrorism, Gabriel Rubin, Christopher Salvatore

Department of Justice Studies Faculty Scholarship and Creative Works

Extensive research has found that there are differences in reported levels of fear of crime and associated protective actions influenced by socio-demographic characteristics such as race and gender. Further studies, the majority of which focused on violent and property crime, have found that specific demographic characteristics influence fear of crime and protective behaviors. However, little research has focused on the influence of socio-demographic characteristics on perceptions, and protective actions in response to the threat of terrorism. Using data from the General Social Survey, this study compared individual-level protective actions and perceptions of the effectiveness of protective responses to the 9 ...


Can We Learn Anything About Pleading Changes From Existing Data?, Jonah B. Gelbach Jan 2015

Can We Learn Anything About Pleading Changes From Existing Data?, Jonah B. Gelbach

Faculty Scholarship at Penn Law

In light of the gateway role that the pleading standard can play in our civil litigation system, measuring the empirical effects of pleading policy changes embodied in the Supreme Court's controversial Twombly and Iqbal cases is important. In my earlier paper, Locking the Doors to Discovery, I argued that in doing so, special care is required in formulating the object of empirical study. Taking party behavior seriously, as Locking the Doors does, leads to empirical results suggesting that Twombly and Iqbal have had substantial effects among cases that face Rule 12(b)(6) motions post-Iqbal. This paper responds ...


Asymmetric Empirical Similarity, Joshua C. Teitelbaum Mar 2014

Asymmetric Empirical Similarity, Joshua C. Teitelbaum

Georgetown Law Faculty Publications and Other Works

The paper offers a formal model of analogical legal reasoning and takes the model to data. Under the model, the outcome of a new case is a weighted average of the outcomes of prior cases. The weights capture precedential influence and depend on fact similarity (distance in fact space) and precedential authority (position in the judicial hierarchy). The empirical analysis suggests that the model is a plausible model for the time series of U.S. maritime salvage cases. Moreover, the results evince that prior cases decided by inferior courts have less influence than prior cases decided by superior courts.


Nudging The Fda, W. Nicholson Price Ii, I. Glenn Cohen Jan 2014

Nudging The Fda, W. Nicholson Price Ii, I. Glenn Cohen

Law Faculty Scholarship

[Excerpt] "The FDA’s regulation of drugs is frequently the subject of policy debate, with arguments falling into two camps. On the one hand, a libertarian view of patients and the health care system holds high the value of consumer choice. Patients should get all the information and the drugs they want; the FDA should do what it can to enforce some basic standards but should otherwise get out of the way. On the other hand, a paternalist view values the FDA’s role as an expert agency standing between patients and a set of potentially dangerous drugs and potentially ...


Measuring Circuit Splits: A Cautionary Note, Aaron-Andrew P. Bruhl Jan 2014

Measuring Circuit Splits: A Cautionary Note, Aaron-Andrew P. Bruhl

Faculty Publications

A number of researchers have recently published new measures of the Supreme Court’s behavior in resolving conflicts in the lower courts. These new measures represent an improvement over prior, cruder approaches, but it turns out that measuring the Court’s resolutions of conflicts is surprisingly difficult. The aim of this methodological comment is to describe those difficulties and to establish several conclusions that follow from them. First, the new measures of the Court’s behavior are certainly imprecise and may reflect biased samples. Second, using the Supreme Court Database, which some studies rely on to assemble a dataset of ...


Lost In Translation: Statistical Inference In Court, Erica Beecher-Monas Jan 2014

Lost In Translation: Statistical Inference In Court, Erica Beecher-Monas

Law Faculty Research Publications

No abstract provided.


Expert Mining And Required Disclosure, Jonah B. Gelbach Jan 2014

Expert Mining And Required Disclosure, Jonah B. Gelbach

Faculty Scholarship at Penn Law

No abstract provided.


An Exploration Of “Non-Economic” Damages In Civil Jury Awards, Herbert M. Kritzer, Guangya Liu, Neil Vidmar Jan 2014

An Exploration Of “Non-Economic” Damages In Civil Jury Awards, Herbert M. Kritzer, Guangya Liu, Neil Vidmar

Faculty Scholarship

Using three primary data sources plus three supplemental sources discussed in an appendix, this paper examines how well non-economic damages could be predicted by economic damages and at how the ratio of non-economic damages to economic damages changed as the magnitude of the economic damages awarded by juries increased. We found a mixture of consistent and inconsistent patterns across our various datasets. One fairly consistent pattern was the tendency for the ratio of non-economic to economic damages to decline as the amount of economic damages increased. Moreover, the variability of the ratio also tended to decline as the amount of ...


Simplicial Complexes Obtained From Qualitative Probability Orders, Paul H. Edelman, Tatiana Gvozdeva, Arkadii Slinko Jan 2013

Simplicial Complexes Obtained From Qualitative Probability Orders, Paul H. Edelman, Tatiana Gvozdeva, Arkadii Slinko

Vanderbilt Law School Faculty Publications

The goal of this paper is to introduce a new class of simplicial complexes that naturally generalize the threshold complexes. These will be derived from qualitative probability orders on subsets of a finite set that generalize subset orders induced by probability measures. We show that this new class strictly contains the threshold complexes and is strictly contained in the shifted complexes. We conjecture that this class of complexes is exactly the set of strongly acyclic complexes, a class that has previously appeared in the context of cooperative games. Beyond the results themselves, this new class of complexes allows us to ...


Consilience: Radiocarbon, Instrumental Neutron Activation Analysis, And Litigation In The Ancestral Caddo Region, Robert Z. Selden Jr. Jan 2013

Consilience: Radiocarbon, Instrumental Neutron Activation Analysis, And Litigation In The Ancestral Caddo Region, Robert Z. Selden Jr.

CRHR: Archaeology

Through the creation and analysis of databases for radiocarbon, instrumental neutron activation analysis (INAA), and law, macro-level trends are exposed that form the framework of a broader research program aimed at advancing ideas of craft specialization and archaeological theory in the ancestral Caddo region of Southwest Arkansas, Northwest Louisiana, Northeast Texas, and Southeast Oklahoma. The findings of this investigation illustrate the research potential that remains buried within the context of cultural resource management (CRM) reports and legal databases (Westlaw and LexisNexis) that is awaiting consumption within regional research designs aimed at exploring the nuances and trends that appear through synthetic ...


Spatial Dynamics Of U.S. Cultural Resource Law, Robert Z. Selden Jr., C. Britt Bousman Jan 2013

Spatial Dynamics Of U.S. Cultural Resource Law, Robert Z. Selden Jr., C. Britt Bousman

CRHR: Archaeology

The American Antiquities Act, Historic Sites Act, Archeological and Historic Preservation Act, National Historic Preservation Act, American Indian Religious Freedom Act, Archeological Resources Protection Act, Abandoned Shipwreck Act, and the Native American Graves Protection and Repatriation Act comprise the basis of our exploration of cultural resource legislation in the United States. Since the passage of the American Antiquities Act in 1906, 1086 cases have challenged these statutes in U.S. courts. We investigate temporal and regional patterns of the case law to establish whether these laws are uniformly prosecuted throughout the U.S. Our findings suggest that case law is ...


Book Review: Burden Of Proof: A Review Of Math On Trial, Paul H. Edelman Jan 2013

Book Review: Burden Of Proof: A Review Of Math On Trial, Paul H. Edelman

Vanderbilt Law School Faculty Publications

In Math on Trial, Leila Schneps and Coralie Col­ mez write about the abuse of mathematical argu­ ments in criminal trials and how these flawed arguments "have sent innocent people to prison" (p. ix). Indeed, people "saw their lives ripped apart by simple mathematical errors." The purpose of focusing on these errors, despite mathematics' "relatively rare use in trials" (p. x), is "that many of the common mathematical fallacies that pervade the public sphere are perfectly represented by these trials. Thus they serve as ideal illustrations of these errors and of the drastic consequences that faulty reasoning has on real ...


When 10 Trials Are Better Than 1000: An Evidentiary Perspective On Trial Sampling, Edward K. Cheng Jan 2012

When 10 Trials Are Better Than 1000: An Evidentiary Perspective On Trial Sampling, Edward K. Cheng

Vanderbilt Law School Faculty Publications

In many mass tort cases, separately trying all individual claims is impractical, and thus a number of trial courts and commentators have explored the use of statistical sampling as a way of efficiently processing claims. Most discussions on the topic, however, implicitly assume that sampling is a “second best” solution: individual trials are preferred for accuracy, and sampling only justified under extraordinary circumstances. This Essay explores whether this assumption is really true. While intuitively one might think that individual trials would be more accurate at estimating liability than extrapolating from a subset of cases, the Essay offers three ways in ...


If The Shoe Fits They Might Acquit: The Value Of Forensic Science Testimony, Jonathan Koehler Jan 2011

If The Shoe Fits They Might Acquit: The Value Of Forensic Science Testimony, Jonathan Koehler

Faculty Working Papers

The probative value of forensic science evidence (such as a shoeprint) varies widely depending on how the evidence and hypothesis of interest is characterized. This paper uses a likelihood ratio (LR) approach to identify the probative value of forensic science evidence. It argues that the "evidence" component should be characterized as a "reported match," and that the hypothesis component should be characterized as "the matching person or object is the source of the crime scene sample." This characterization of the LR forces examiners to incorporate risks from sample mix-ups and examiner error into their match statistics. But how will legal ...


Probabilities In Probable Cause And Beyond: Statistical Versus Concrete Harms, Sherry F. Colb Jul 2010

Probabilities In Probable Cause And Beyond: Statistical Versus Concrete Harms, Sherry F. Colb

Cornell Law Faculty Publications

No abstract provided.


U.S. Chamber Of Commerce Liability Survey: Inaccurate, Unfair, And Bad For Business, Theodore Eisenberg Dec 2009

U.S. Chamber Of Commerce Liability Survey: Inaccurate, Unfair, And Bad For Business, Theodore Eisenberg

Cornell Law Faculty Publications

The U.S. Chamber of Commerce uses its Survey of State Liability to criticize judiciaries and seek legal change but no detailed evaluation of the survey’s quality exists. This article presents evidence that the survey is substantively inaccurate and methodologically flawed. It incorrectly characterizes state law; respondents provide less than 10 percent correct answers for objectively verifiable responses. It is internally inconsistent; a state threatened with judicial hellhole status ranked first in the survey while venues not on the list ranked lower. The absence of correlation between survey rankings and observable activity suggests that other factors drive the rankings ...


Comments On "Getting Scarred And Winning Lotteries: Effects Of Exemplar Cuing And Statistical Format On Imagining Low-Probability Events," By Newell, Mitchell, And Hayes (2008), Jonathan Koehler, Laura Macchi Jan 2009

Comments On "Getting Scarred And Winning Lotteries: Effects Of Exemplar Cuing And Statistical Format On Imagining Low-Probability Events," By Newell, Mitchell, And Hayes (2008), Jonathan Koehler, Laura Macchi

Faculty Working Papers

Newell, Mitchell, and Hayes (NMH) conduct three experiments designed to test whether exemplar cuing (EC) theory or a statistical format theory provides a more accurate account for how people make judgments about low-probability events. They report finding support for the statistical format theory and little or no support for EC. However, NMH misstate the requirements for the production of exemplars in EC theory. As a result, they confuse non-exemplar conditions with exemplar conditions in their experiments, and find results that are virtually irrelevant to EC theory.