The equivalence of three latent class models and ML estimators

The purpose of this letter is to show the equivalence of three latent class models; the switching regression model with endogenous switching and a latent outcome (the binary Roy model), the probit model with a systematically misclassified dependent variable, and a trivariate probit model with partial observability. The probit model with measurement error is an enhanced version of existing models which allows for the potential correlation between error terms. Establishing this connection, we hope, will help a researcher working on one of these classes of estimators to benefit from the literature and software related to other families

Measurement Invariance and Response Bias: A Stochastic Frontier Approach

The goals of the present paper were to assess measurement invariance using a common econometric method and to illustrate the approach with self-reported measures of parenting behaviors before and after a family intervention. Most recent literature on measurement invariance (MI) in psychological research 1) explores the use of structural equation modeling (SEM) and confirmatory factor analysis to identify measurement invariance, and 2) tests for measurement invariance across groups rather than across time. We use method, Stochastic Frontier Estimation, or SFE, to identify response bias and covariates of response bias both across individuals at a single point in time and across two measurement occasions (before and after participation in a family intervention). We examined the effects of participant demographics (N = 1437) on response bias; gender and race/ethnicity were related to magnitude of bias and to changes in bias across time, and bias was lower at posttest than at pretest. We discuss analytic advantages and disadvantages of SFE relative to SEM approaches and note that the technique may be particularly useful in addressing the problem of “response shift bias” or “recalibration” in program evaluation -- that is, a shift in metric from before to after an intervention which is caused by the intervention itself and may lead to underestimates of program effects.Measurement invariance, measurement equivalence, response bias, response-shift bias, stochastic frontier analysis

The Pot Calling the Kettle Black? A Comparison of Measures of Current Tobacco Use

Researchers often use the discrepancy between self-reported and biochemically assessed active smoking status to argue that self-reported smoking status is not reliable, ignoring the limitations of biochemically assessed measures and treating it as the gold standard in their comparisons. Here, we employ econometric techniques to compare the accuracy of self-reported and biochemically assessed current tobacco use, taking into account measurement errors with both methods. Our approach allows estimating and comparing the sensitivity and specificity of each measure without directly observing true smoking status. The results, robust to several alternative specifications, suggest that there is no clear reason to think that one measure dominates the other in accuracy

Estimating treatment effectiveness with sample selection

We consider a situation where treatment outcome is observed after two stages of selection; first of participation into the treatment, then in completion of the treatment. Estimates were obtained using two methods. First, three different binary response selection models were estimated sequentially in multiple steps. Second, all three equations were estimated jointly. All methods produce similar parameter estimates. We find evidence of selection effects from completion to outcome that could bias parameter estimates of the outcome equation, but not from participation to outcome, indicating that correcting only for participation may be insufficient to avoid biased estimates in the outcome equation.selection bias, trivariate probit, bivariate probit, treatment effects

Dirty hands on troubled waters: Sanitation, access to water and child health in Ethiopia

In this paper, we investigate the impact of access to drinking water sources and sanitation facilities on the incidence of diarrheal diseases among children below 5 years of age in Ethiopia using the propensity score matching technique with a polychotomous treatment variable. We find that among the water sources traditionally considered as improved, only water piped into dwelling, yard or plot leads to a large percentage point reduction in diarrhea incidence. The other water sources, generally believed as clean, are not effective in reducing diarrhea even compared with some of the unimproved water sources. We also find that some unimproved water sources and sanitation facilities are less inferior than they are believed to be. These results suggest that the traditional way of categorizing different types of improved and unimproved water sources and sanitation facilities into a dichotomous variable, “improved” or “unimproved”, could be misleading as it masks the heterogeneous effects of the water sources and the sanitation facilities

Research and Reflective Practice in the ESL Classroom: Voices from Sri Lanka

Modern language education favours the model of a reflective teacher-researcher who is engaged in both individual and collaborative curriculum revision and teaching-learning environment improvement. The present paper addresses the issue of classroom research and reflective practice in current ESL pedagogy and teacher professional development. The theoretical introduction is followed by research findings recently gathered from Sri Lankan ESL teachers. The study aimed at ascertaining the extent to which Sri Lankan ESL teachers are involved in classroom research and discussing various reasons why they assume or do not assume the role of a teacher-researcher. The study reports interesting findings, calling for a wide-ranging discussion on reflective inquiry in the language classroom as theory and practice seem to be marching to a different tune

Structure of the Mouse Myelin P 2 Protein Gene

Myelin P 2 protein is a small (14,800 Da) protein found in peripheral and central nervous system myelin. To investigate the regulation of expression of this myelin protein, a mouse genomic library was screened with a rabbit P 2 cDNA (pSN2.2–2), and a single positive phage clone containing a 20-kb insert was obtained. This insert contained a single internal Sail restriction site and several Eco RI sites. The Eco RI fragments from this insert were subcloned into Bluescript. The rabbit P 2 cDNA (pSN2.2–2) hybridized with a 4-kb Eco RI fragment, and this 4-kb fragment was then sequenced after the creation of nested deletions. The mouse gene contained four exons: exon 1 coded for amino acids 1–24, exon 2 for amino acids 24–81, exon 3 for amino acids 82–115, and exon 4 for amino acids 116–131. The three introns were 1.2 kb, 150 bp, and 1.3 kb in length. Primer extension analysis revealed two transcription start sites at +1 and +47, consistent with the presence of two P 2 mRNAs, with the larger transcript appearing more abundant. The amino acid sequences predicted from the mouse DNA indicate that the mouse protein differs from the rabbit protein at 16 different positions, with most of the differences located in exon 3. When the gene structure of fatty acid binding protein (FABP) genes were compared, the P 2 gene had the same overall structure as others in the FABP family, suggesting a common ancestral gene for members of this family. The 5′-flanking region contains candidate TATA and CAAT sequences, as well as two AP-l binding sites that may be important in modulation of the expression of this gene.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65134/1/j.1471-4159.1991.tb02101.x.pd

SRI LANKA’S STRENGTH AS AN INTERNATIONAL INDUSTRIAL LOCATION: A THEORETICAL EXAMINATION

Sri Lanka, in 1978, introduced outward looking export oriented industrialization (OL-EOI) policy with heavy reliance on foreign direct investment (FDI) against the three decade long inward looking import substitution industrialization (IL-ISI) policy that had caused serious impediments to economic development. Although four decades have passed since then, theoretically founded analyses to assess Sri Lanka’s locational soundness are scarce. Thus, this study adopts the Investment Development Path (IDP) framework of John Dunning and Rajnish Narula (1996) for assessing the strength of Sri Lanka as an international industrial location. This study primarily traces the investment development path of Sri Lanka for the past seven decades (1950-2015) covering two policy regimes, namely; relatively closed economic policy regime (1950-1977) and the open economic policy regime (1978-2015). The findings reveal that Sri Lanka has only been able to reach the early second stage of the IDP. This fact can be appropriated to insignificant FDI inflows in consequent to meager supply of location specific created assets (Lca) in contrast to heavy reliance on location specific natural assets (Lna).Keywords: Foreign Direct Investment, Investment Development Path, location specific natural assets, location specific created asset

LEPR c.668A>G polymorphism in a cohort of Sri Lankan women with pre-eclampsia / pregnancy induced hypertension: a case control study

BACKGROUND: Leptin is known to be elevated in pre-eclampsia/ pregnancy induced hypertension (PE/PIH). However the reports on the association of leptin receptor (LEPR) c.668A>G polymorphism with PE/PIH are inconsistent. FINDINGS: LEPR c.668A>G polymorphism was studied in a cohort of women with PE/PIH (N = 61) and normotensive pregnancies (N = 40) by polymerase chain reaction / restriction fragment length polymorphism. Genotype and allele frequencies were in Hardy-Weinberg equilibrium within both groups (Chi square test). Allele and genotype frequencies were not significantly different between PE/PIH and normotensive pregnancies (Chi square test). Leptin levels (Kruskal Wallis analysis of variance) and leptin/body mass index (one way analysis of variance) were not significantly different between genotypes within each group. However, leptin (Mann Whitney U test) and leptin normalised to body mass index (unpaired t test) were significantly higher in PE/PIH women homozygous and heterozygous for the G668 allele than in respective normotensives. CONCLUSIONS: Whether the leptin receptor c.668A>G polymorphism increases the risk of developing PE/PIH in Sri Lankan women remains inconclusive in view of the smaller sample studied. However leptin levels in PE/PIH appeared to be modulated by this polymorphism

Partial Structure and Mapping of the Human Myelin P 2 Protein Gene

The myelin P 2 protein, a 14,800-Da cytosolic protein found primarily in peripheral nerves, belongs to a family of fatty acid binding proteins. Although it is similar in amino acid sequence and tertiary structure to fatty acid binding proteins found in the liver, adipocytes, and intestine, its expression is limited to the nervous system. It is detected only in myelin-producing cells of the central and peripheral nervous systems, i.e., the oligodendrocytes and Schwann cells, respectively. As part of a program to understand the regulation of expression of this gene, to determine its function in myelin-producing cells, and to study its role in peripheral nerve disease, we have isolated and characterized overlapping human genomic clones encoding the P 2 protein. We report here on the partial structure of this gene, and on its localization within the genome. By using a panel of human-hamster somatic cell hybrids and by in situ hybridization, we have mapped the human P 2 gene to segment q21 on the long arm of chromosome 8. This result identifies the myelin P 2 gene as a candidate gene for autosomal recessive Charcot-Marie-Tooth disease type 4A.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65484/1/j.1471-4159.1994.63062010.x.pd