Is EM really necessary here? Examples where it seems simpler not to use EM

AStA Advances in Statistical Analysis - If one is to judge by counts of citations of the fundamental paper (Dempster in JRSSB 39: 1–38, 1977), EM algorithms are a runaway success. But it is...     

A response to M. Stone: 'How not to measure the efficiency of public services (and how one might)'

Summary.  This is a response to Stone's criticisms of the Spottiswoode report to the UK Treasury which was responding to the Treasury's request for improved methods to evaluate the efficiency and productivity of the 43 police districts in England and Wales. The Spottiswoode report recommended uses of data envelopment analysis (DEA) and stochastic frontier analysis (SFA), which Stone critiqued en route to proposing an alternative approach. Here we note some of the most serious errors in his criticism and inaccurate portrayals of DEA and SFA. Most of our attention is devoted to DEA, and to Stone's recommended alternative approach without much attention to SFA, partly because of his abbreviated discussion of the latter. In our response we attempt to be constructive as well as critical by showing how Stone's proposed approach can be joined to DEA to expand his proposal beyond limitations in his formulations.     

The impact of missing data and how it is handled on the rate of false-positive results in drug development

In drug development, a common choice for the primary analysis is to assess mean changes via analysis of (co)variance with missing data imputed by carrying the last or baseline observations forward (LOCF, BOCF). These approaches assume that data are missing completely at random (MCAR). Multiple imputation (MI) and likelihood-based repeated measures (MMRM) are less restrictive as they assume data are missing at random (MAR). Nevertheless, LOCF and BOCF remain popular, perhaps because it is thought that the bias in these methods lead to protection against falsely concluding that a drug is more effective than the control. We conducted a simulation study that compared the rate of false positive results or regulatory risk error (RRE) from BOCF, LOCF, MI, and MMRM in 32 scenarios that were generated from a 2(5) full factorial arrangement with data missing due to a missing not at random (MNAR) mechanism. Both BOCF and LOCF inflated RRE were compared to MI and MMRM. In 12 of the 32 scenarios, BOCF yielded inflated RRE compared with eight scenarios for LOCF, three scenarios for MI and four scenarios for MMRM. In no situation did BOCF or LOCF provide adequate control of RRE when MI and MMRM did not. Both MI and MMRM are better choices than either BOCF or LOCF for the primary analysis.     

Mediterranean house sparrows ( Passer domesticus ) are not used to freezing temperatures: An analysis of survival rates

It has been suggested that house sparrows ( Passer domesticus ) are adapted to the mean local weather conditions, and that sudden and severe departures from these conditions (e.g. persistent subfreezing temperatures) can exert an important mortality in the population. Here we test this at a Mediterranean locality in NE Spain, where the typical very mild climate was disturbed in 1984-1985 by a very severe winter. The capture-recapture data were recorded from 1980 to 1986 ( n = 2021 marked individuals, 309 associated recaptures). Using program SURGE, we examined the relationship between annual survival and number of days when temperature fell below freezing, total precipitation from October to March (i.e. winter) and from April to September (i.e. breeding), sum of the low monthly minimum temperatures from October to March, and sum of the high monthly maximum temperatures from April to September. Number of freezing days accounted for most of the variation in survival rates, which declined from 0.50-0.40 in mild and normal years, respectively, to 0.17 in 1984-1985 when January temperatures dropped below 0 degrees C for 12 days.     

世界经济增长率的测度以及中国贡献的分析

 摘　　要:国际上常用的世界经济增长率测算方法有按汇率法或按购买力平价（PPPs）法加权的连锁加权法和固定基期法。不同方法测算出不同的数据结果。它们各有优缺点和独特的经济含义，满足不同的经济研究目的需要。统计数据分析表明，按PPPs法加权的世界经济增长率要明显高于汇率法加权的结果。不论按何种方法测算，自1980年以来，中国对全球经济发展的贡献不断增大，现已成为拉动世界经济增长的重要引擎     

GDP RIP (1933–2010)

When a nation's Gross Domestic Product goes up, politicians glow with pride. When it goes down, headlines shout doom. Yet GDP says nothing about the real health of a nation. It measures nobody's happiness; it tells no one how much we are destroying our environment or our children's future. It ignores all the important measures of human life. Nic Marks says it is time we replaced this outmoded measurement with something more useful.     

Small populations of the north: their problems and how to solve them

The authors examine the present conditions of 26 small, isolated populations living in the north of Russia. The total size of the population under consideration is 181,600, according to the 1989 Soviet census. The conclusion is that these populations are under severe threat of extinction and that there is no consensus about how to resolve their present predicament.     

Wilcoxon's signed‐rank statistic: what null hypothesis and why it matters

In statistical literature, the term ‘signed‐rank test’ (or ‘Wilcoxon signed‐rank test’) has been used to refer to two distinct tests: a test for symmetry of distribution and a test for the median of a symmetric distribution, sharing a common test statistic. To avoid potential ambiguity, we propose to refer to those two tests by different names, as ‘test for symmetry based on signed‐rank statistic’ and ‘test for median based on signed‐rank statistic’, respectively. The utility of such terminological differentiation should become evident through our discussion of how those tests connect and contrast with sign test and one‐sample t‐test. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.