Simple Inference on Functionals of Set-Identified Parameters Defined by Linear Moments

This paper considers uniformly valid (over a class of data generating processes) inference for linear functionals of partially identified parameters in cases where the identified set is defined by linear (in the parameter) moment inequalities. We propose a bootstrap procedure for constructing uniformly valid confidence sets for a linear functional of a partially identified parameter. The proposed method amounts to bootstrapping the value functions of a linear optimization problem, and subsumes subvector inference as a special case. In other words, this paper shows the conditions under which ``naively'' bootstrapping a linear program can be used to construct a confidence set with uniform correct coverage for a partially identified linear functional. Unlike other proposed subvector inference procedures, our procedure does not require the researcher to repeatedly invert a hypothesis test, and is extremely computationally efficient. In addition to the new procedure, the paper also discusses connections between the literature on optimization and the literature on subvector inference in partially identified models

The Usefulness of Cap-assisted Endoscopic Retrograde Cholangiopancreatography for Cannulation Complicated by a Periampullary Diverticulum

Endoscopic retrograde cholangiopancreatography (ERCP) is an advanced therapeutic procedure to manage choledocholithiasis and pancreatobiliary malignancy. On occasion, ERCP failure is encountered due to difficulties in cannulation. We assessed the safety and feasibility of cap-assisted ERCP via analyzing cases in which cannulation was complicated by periampullary diverticulum. Between November 2013 and March 2014, ERCP procedures were performed in 346 patients in our tertiary medical center. Among the 73 patients who had a periampullary diverticulum, conventional ERCP failed in 5 patients due to hidden papilla (n=3) or use of tangential approach (n=2). As a rescue method, needle knife fistulotomy and selective biliary cannulation using cap-fitted forward-viewing endoscopy were successfully used in 4 patients without major complications. Based on our experience, cap-fitted forward-viewing endoscopy was relatively easy to measure the exact position of papilla and to perform biliary cannulation properly. Therefore, we recommend using cap-assisted ERCP by forward-viewing endoscopy as a useful and safe alternative to manage patients in whom cannulation is complicated by periampullary diverticulum