Posts Tagged With: Nathan Schachtman

PhilStatLaw: Reference Manual on Scientific Evidence (3d ed) on Statistical Significance (Schachtman)

Memory Lane: One Year Ago on error statistics.com

A quick perusal of the “Manual” on Nathan Schachtman’s legal blog shows it to be chock full of revealing points of contemporary legal statistical philosophy.  The following are some excerpts, read the full blog here.   I make two comments at the end.

July 8th, 2012

Nathan Schachtman

How does the new Reference Manual on Scientific Evidence (RMSE3d 2011) treat statistical significance?  Inconsistently and at times incoherently.

Professor Berger’s Introduction

In her introductory chapter, the late Professor Margaret A. Berger raises the question of the role statistical significance should play in evaluating a study’s support for causal conclusions:

“What role should statistical significance play in assessing the value of a study? Epidemiological studies that are not conclusive but show some increased risk do not prove a lack of causation. Some courts find that they therefore have some probative value, 62 at least in proving general causation. 63”

Margaret A. Berger, “The Admissibility of Expert Testimony,” in RMSE3d 11, 24 (2011).

This seems rather backwards.  Berger’s suggestion that inconclusive studies do not prove lack of causation seems nothing more than a tautology.  And how can that tautology support the claim that inconclusive studies “therefore ” have some probative value? This is a fairly obvious logical invalid argument, or perhaps a passage badly in need of an editor.

…………

Chapter on Statistics

The RMSE’s chapter on statistics is relatively free of value judgments about significance probability, and, therefore, a great improvement upon Berger’s introduction.  The authors carefully describe significance probability and p-values, and explain:

“Small p-values argue against the null hypothesis. Statistical significance is determined by reference to the p-value; significance testing (also called hypothesis testing) is the technique for computing p-values and determining statistical significance.”

David H. Kaye and David A. Freedman, “Reference Guide on Statistics,” in RMSE3d 211, 241 (3ed 2011).  Although the chapter confuses and conflates Fisher’s interpretation of p-values with Neyman’s conceptualization of hypothesis testing as a dichotomous decision procedure, this treatment is unfortunately fairly standard in introductory textbooks.

Kaye and Freedman, however, do offer some important qualifications to the untoward consequences of using significance testing as a dichotomous outcome:

“Artifacts from multiple testing are commonplace. Because research that fails to uncover significance often is not published, reviews of the literature may produce an unduly large number of studies finding statistical significance.111 Even a single researcher may examine so many different relationships that a few will achieve statistical significance by mere happenstance. Almost any large data set—even pages from a table of random digits—will contain some unusual pattern that can be uncovered by diligent search. Having detected the pattern, the analyst can perform a statistical test for it, blandly ignoring the search effort. Statistical significance is bound to follow.

There are statistical methods for dealing with multiple looks at the data, which permit the calculation of meaningful p-values in certain cases.112 However, no general solution is available, and the existing methods would be of little help in the typical case where analysts have tested and rejected a variety of models before arriving at the one considered the most satisfactory (see infra Section V on regression models). In these situations, courts should not be overly impressed with claims that estimates are significant. Instead, they should be asking how analysts developed their models.113 ”

Id. at 256 -57.  This qualification is omitted from the overlapping discussion in the chapter on epidemiology, where it is very much needed. Continue reading

Categories: P-values, PhilStatLaw, significance tests | Tags: , , , , | 6 Comments

PhilStatLaw: Infections in the court

Nathan Schachtman appropriately refers to the way in which “dicta infects Daubert” in his latest blogpost Siracusano Dicta Infects Daubert Decisions. Here the “dicta” (or dictum?) is a throwaway remark on (lack of) statistical significance and causal inference by the Supreme Court, in an earlier case involving the drug company Matrixx (Matrixx Initiatives, Inc. v. Siracusano). As I note in my post of last Feb,

“the ruling had nothing to do with what’s required to show cause and effect, but only what information a company is required to reveal to its shareholders in order not to mislead them (as regards information that could be of relevance to them in their cost-benefit assessments of the stock’s value and future price).”(See “Distortions in the Court”)

obiter dicta

  1. A judge’s incidental expression of opinion, not essential to the decision and not establishing precedent.
  2. An incidental remark.

It was already surprising that the Supreme Court took up that earlier case; the way they handled the irrelevant statistical issues was more so. Continue reading

Categories: PhilStatLaw, Statistics | Tags: , , , , | 5 Comments

PhilStatLaw: Reference Manual on Scientific Evidence (3d ed) on Statistical Significance (Schachtman)

A quick perusal of the “Manual” on Nathan Schachtman’s legal blog shows it to be chock full of revealing points of contemporary legal statistical philosophy.  The following are some excerpts, read the full blog here.   I make two comments at the end.

July 8th, 2012

Nathan Schachtman

How does the new Reference Manual on Scientific Evidence (RMSE3d 2011) treat statistical significance?  Inconsistently and at times incoherently.

Professor Berger’s Introduction

In her introductory chapter, the late Professor Margaret A. Berger raises the question of the role statistical significance should play in evaluating a study’s support for causal conclusions:

“What role should statistical significance play in assessing the value of a study? Epidemiological studies that are not conclusive but show some increased risk do not prove a lack of causation. Some courts find that they therefore have some probative value, 62 at least in proving general causation. 63”

Margaret A. Berger, “The Admissibility of Expert Testimony,” in RMSE3d 11, 24 (2011).

This seems rather backwards.  Berger’s suggestion that inconclusive studies do not prove lack of causation seems nothing more than a tautology.  And how can that tautology support the claim that inconclusive studies “therefore ” have some probative value? This is a fairly obvious logical invalid argument, or perhaps a passage badly in need of an editor.

…………

Chapter on Statistics

The RMSE’s chapter on statistics is relatively free of value judgments about significance probability, and, therefore, a great improvement upon Berger’s introduction.  The authors carefully describe significance probability and p-values, and explain:

“Small p-values argue against the null hypothesis. Statistical significance is determined by reference to the p-value; significance testing (also called hypothesis testing) is the technique for computing p-values and determining statistical significance.”

David H. Kaye and David A. Freedman, “Reference Guide on Statistics,” in RMSE3d 211, 241 (3ed 2011).  Although the chapter confuses and conflates Fisher’s interpretation of p-values with Neyman’s conceptualization of hypothesis testing as a dichotomous decision procedure, this treatment is unfortunately fairly standard in introductory textbooks.

Kaye and Freedman, however, do offer some important qualifications to the untoward consequences of using significance testing as a dichotomous outcome: Continue reading

Categories: Statistics | Tags: , , , , | 9 Comments

Statistical Science Court?

Nathan Schactman has an interesting blog post onScientific illiteracy among the judiciary”:

February 29th, 2012

Ken Feinberg, speaking at a symposium on mass torts, asks what legal challenges do mass torts confront in the federal courts. The answer seems obvious.

Pharmaceutical cases that warrant federal court multi-district litigation (MDL) treatment typically involve complex scientific and statistical issues. The public deserves having MDL cases assigned to judges who have special experience and competence to preside in cases in which these complex issues predominate. There appears to be no procedural device to ensure that the judges selected in the MDL process have the necessary experience and competence, and a good deal of evidence to suggest that the MDL judges are not up to the task at hand.

In the aftermath of the Supreme Court’s decision in Daubert, the Federal Judicial Center assumed responsibility for producing science and statistics tutorials to help judges grapple with technical issues in their cases. The Center has produced videotaped lectures as well as the Reference Manual on Scientific Evidence, now in its third edition. Despite the Center’s best efforts, many federal judges have shown themselves to be incorrigible. It is time to revive the discussions and debates about implementing a “science court.”

I am intrigued to hear Schachtman revive the old and controversial idea of a “science court”, although it has actually never left, but has come up for debate every few years for the past 35 or 40 years! In the 80s, it was a hot topic in the new “science and values” movement, but I do not think it was ever really put to an adequate experimental test. The controversy directly relates to the whole issue of distinguishing evidential and policy issues (in evidence-based policy), Continue reading
Categories: philosophy of science, PhilStatLaw, Statistics | Tags: , , , , | 2 Comments

Guest Blogger: Interstitial Doubts About the Matrixx

By: Nathan Schachtman, Esq., PC*

When the Supreme Court decided this case, I knew that some people would try to claim that it was a decision about the irrelevance or unimportance of statistical significance in assessing epidemiologic data. Indeed, the defense lawyers invited this interpretation by trying to connect materiality with causation. Having rejected that connection, the Supreme Court’s holding could address only materiality because causation was never at issue. It is a fundamental mistake to include undecided, immaterial facts as part of a court’s holding or the ratio decidendi of its opinion.

Interstitial Doubts About the Matrixx 

Statistics professors are excited that the United States Supreme Court issued an opinion that ostensibly addressed statistical significance. One such example of the excitement is an article, in press, by Joseph B. Kadane, Professor in the Department of Statistics, in Carnegie Mellon University, Pittsburgh, Pennsylvania. See Joseph B. Kadane, “Matrixx v. Siracusano: what do courts mean by ‘statistical significance’?” 11[x] Law, Probability and Risk 1 (2011).

Professor Kadane makes the sensible point that the allegations of adverse events did not admit of an analysis that would imply statistical significance or its absence. Id. at 5. See Schachtman, “The Matrixx – A Comedy of Errors” (April 6, 2011)”; David Kaye, ” Trapped in the Matrixx: The U.S. Supreme Court and the Need for Statistical Significance,” BNA Product Safety and Liability Reporter 1007 (Sept. 12, 2011). Unfortunately, the excitement has obscured Professor Kadane’s interpretation of the Court’s holding, and has led him astray in assessing the importance of the case. Continue reading

Categories: Statistics | Tags: , , , , , , | 8 Comments

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