Positive Average Effect Research Articles

A Meta–Analytic and Conceptual Update on the Associations between Procrastination and Multidimensional Perfectionism

The equivocal and debated findings from a 2007 meta–analysis, which viewed perfectionism as a unidimensional construct, suggested that perfectionism was unrelated to procrastination. The present meta–analysis aimed to provide a conceptual update and reanalysis of the procrastination–perfectionism association guided by both a multidimensional view of perfectionism and self–regulation theory. The random–effects meta–analyses revealed a small to medium positive average effect size ( r = .23; k = 43, N = 10 000; 95% confidence interval (95% CI) [0.19, 0.27]) for trait procrastination and perfectionistic concerns and a small to medium negative average effect size ( r = −.22; k = 38, N = 9544; 95% CI [−0.26, −0.18]) for procrastination and perfectionistic strivings. The average correlations remained significant after statistically accounting for the joint variance between the two perfectionism dimensions via semi–partial correlations. For perfectionistic concerns, but not perfectionistic strivings, the effects depended on the perfectionism measure used. All effects did not vary by the trait procrastination measure used or the respondent's sex. Our findings confirm that from a multidimensional perspective, trait procrastination is both positively and negatively associated with higher–order perfectionism dimensions and further highlights the value of a self–regulation perspective for understanding the cognitive, affective and behavioural dynamics that characterise these traits. Copyright © 2017 European Association of Personality Psychology

Thermal treatment and leaching of biochar alleviates plant growth inhibition from mobile organic compounds.

Recent meta-analyses of plant responses to biochar boast positive average effects of between 10 and 40%. Plant responses, however, vary greatly across systems, and null or negative biochar effects are increasingly reported. The mechanisms responsible for such responses remain unclear. In a glasshouse experiment we tested the effects of three forestry residue wood biochars, applied at five dosages (0, 5, 10, 20, and 50 t/ha) to a temperate forest drystic cambisol as direct surface applications and as complete soil mixes on the herbaceous pioneers Lolium multiflorum and Trifolium repens. Null and negative effects of biochar on growth were found in most cases. One potential cause for null and negative plant responses to biochar is plant exposure to mobile compounds produced during pyrolysis that leach or evolve following additions of biochars to soil. In a second glasshouse experiment we examined the effects of simple leaching and heating techniques to ameliorate potentially phytotoxic effects of volatile and leachable compounds released from biochar. We used Solid Phase Microextraction (SPME)–gas chromatography–mass spectrometry (GC-MS) to qualitatively describe organic compounds in both biochar (through headspace extraction), and in the water leachates (through direct injection). Convection heating and water leaching of biochar prior to application alleviated growth inhibition. Additionally, growth was inhibited when filtrate from water-leached biochar was applied following germination. SPME-GC-MS detected primarily short-chained carboxylic acids and phenolics in both the leachates and solid chars, with relatively high concentrations of several known phytotoxic compounds including acetic acid, butyric acid, 2,4-di-tert-butylphenol and benzoic acid. We speculate that variable plant responses to phytotoxic organic compounds leached from biochars may largely explain negative plant growth responses and also account for strongly species-specific patterns of plant responses to biochar amendments in short-term experiments.

Learning in One-to-One Laptop Environments

Over the past decade, the number of one-to-one laptop programs in schools has steadily increased. Despite the growth of such programs, there is little consensus about whether they contribute to improved educational outcomes. This article reviews 65 journal articles and 31 doctoral dissertations published from January 2001 to May 2015 to examine the effect of one-to-one laptop programs on teaching and learning in K–12 schools. A meta-analysis of 10 studies examines the impact of laptop programs on students’ academic achievement, finding significantly positive average effect sizes in English, writing, mathematics, and science. In addition, the article summarizes the impact of laptop programs on more general teaching and learning processes and perceptions as reported in these studies, again noting generally positive findings.

Cost-effectiveness of telehealth for patients with depression: evidence from the Healthlines randomised controlled trial.

BackgroundDepression is a prevalent long-term condition that is associated with substantial resource use. Telehealth may offer a cost-effective means of supporting the management of people with depression.AimsTo investigate the cost-effectiveness of a telehealth intervention (‘Healthlines') for patients with depression.MethodA prospective patient-level economic evaluation conducted alongside a randomised controlled trial. Patients were recruited through primary care, and the intervention was delivered via a telehealth service. Participants with a confirmed diagnosis of depression and PHQ-9 score ≥10 were recruited from 43 English general practices. A series of up to 10 scripted, theory-led, telephone encounters with health information advisers supported participants to effect a behaviour change, use online resources, optimise medication and improve adherence. The intervention was delivered alongside usual care and was designed to support rather than duplicate primary care. Cost-effectiveness from a combined health and social care perspective was measured by net monetary benefit at the end of 12 months of follow-up, calculated from incremental cost and incremental quality-adjusted life years (QALYs). Cost–consequence analysis included cost of lost productivity, participant out-of-pocket expenditure and the clinical outcome.ResultsA total of 609 participants were randomised – 307 to receive the Healthlines intervention plus usual care and 302 to receive usual care alone. Forty-five per cent of participants had missing quality of life data, 41% had missing cost data and 51% of participants had missing data on either cost or utility, or both. Multiple imputation was used for the base-case analysis. The intervention was associated with incremental mean per-patient National Health Service/personal social services cost of £168 (95% CI £43 to £294) and an incremental QALY gain of 0.001 (95% CI −0.023 to 0.026). The incremental cost-effectiveness ratio was £132 630. Net monetary benefit at a cost-effectiveness threshold of £20 000 was −£143 (95% CI −£164 to −£122) and the probability of the intervention being cost-effective at this threshold value was 0.30. Productivity costs were higher in the intervention arm, but out-of-pocket expenses were lower.ConclusionsThe Healthlines service was acceptable to patients as a means of condition management, and response to treatment after 4 months was higher for participants randomised to the intervention. However, the positive average intervention effect size was modest, and incremental costs were high relative to a small incremental QALY gain at 12 months. The intervention is not likely to be cost-effective in its current form.Declaration of interestNone.Copyright and usage© The Royal College of Psychiatrists 2016. This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY) licence.

Deep and surface learning in problem-based learning: a review of the literature.

In problem-based learning (PBL), implemented worldwide, students learn by discussing professionally relevant problems enhancing application and integration of knowledge, which is assumed to encourage students towards a deep learning approach in which students are intrinsically interested and try to understand what is being studied. This review investigates: (1) the effects of PBL on students’ deep and surface approaches to learning, (2) whether and why these effects do differ across (a) the context of the learning environment (single vs. curriculum wide implementation), and (b) study quality. Studies were searched dealing with PBL and students’ approaches to learning. Twenty-one studies were included. The results indicate that PBL does enhance deep learning with a small positive average effect size of .11 and a positive effect in eleven of the 21 studies. Four studies show a decrease in deep learning and six studies show no effect. PBL does not seem to have an effect on surface learning as indicated by a very small average effect size (.08) and eleven studies showing no increase in the surface approach. Six studies demonstrate a decrease and four an increase in surface learning. It is concluded that PBL does seem to enhance deep learning and has little effect on surface learning, although more longitudinal research using high quality measurement instruments is needed to support this conclusion with stronger evidence. Differences cannot be explained by the study quality but a curriculum wide implementation of PBL has a more positive impact on the deep approach (effect size .18) compared to an implementation within a single course (effect size of −.05). PBL is assumed to enhance active learning and students’ intrinsic motivation, which enhances deep learning. A high perceived workload and assessment that is perceived as not rewarding deep learning are assumed to enhance surface learning.

Bounds on Treatment Effects in the Presence of Sample Selection and Noncompliance: The Wage Effects of Job Corps

Randomized and natural experiments are commonly used in economics and other social science fields to estimate the effect of programs and interventions. Even when employing experimental data, assessing the impact of a treatment is often complicated by the presence of sample selection (outcomes are only observed for a selected group) and noncompliance (some treatment group individuals do not receive the treatment while some control individuals do). We address both of these identification problems simultaneously and derive nonparametric bounds for average treatment effects within a principal stratification framework. We employ these bounds to empirically assess the wage effects of Job Corps (JC), the most comprehensive and largest federally funded job training program for disadvantaged youth in the United States. Our results strongly suggest positive average effects of JC on wages for individuals who comply with their treatment assignment and would be employed whether or not they enrolled in JC (the “always-employed compliers”). Under relatively weak monotonicity and mean dominance assumptions, we find that this average effect is between 5.7% and 13.9% 4 years after randomization, and between 7.7% and 17.5% for non-Hispanics. Our results are consistent with larger effects of JC on wages than those found without adjusting for noncompliance.

Tariff Liberalisation, Price Transmission and Rural Welfare in China

AbstractChina's tariff liberalisation as part of its WTO accession application and eventual agreement has been thoroughly analysed in the literature. However, much of this literature is based on forward‐looking ex‐ante analyses and few studies provide empirical evidence on its actual impact. We fill in this gap by evaluating empirically the welfare effects of China's actual tariff liberalisation on Chinese farmers during the 1997–2010 period. By estimating the domestic market price effects of China's tariff liberalisation and the associated wage earning effects, we find that on average Chinese farmers were able to gain more from reduced consumption prices than they would lose from reduced agricultural and wage income due to tariff liberalisation. Welfare gains over time are estimated to be positively correlated with the actual degrees of tariff liberalisation, implying that relatively more gains were realized immediately before and after China's WTO accession in 2001, as compared to the more recent period when relatively little liberalisation was carried out. Farmers’ rising non‐agricultural income and increasing consumption shares of non‐agricultural products are important determinants of these positive average welfare effects. Moreover, welfare gains from tariff liberalisation are shown to be distributed unevenly across Chinese provinces and income levels, with farmers located in coastal provinces and at higher income levels gaining more than their counterparts in remote provinces and at lower income levels.

The World Health Organization's Health Promoting Schools framework: a Cochrane systematic review and meta-analysis.

BackgroundHealthy children achieve better educational outcomes which, in turn, are associated with improved health later in life. The World Health Organization’s Health Promoting Schools (HPS) framework is a holistic approach to promoting health and educational attainment in school. The effectiveness of this approach has not yet been rigorously reviewed.MethodsWe searched 20 health, education and social science databases, and trials registries and relevant websites in 2011 and 2013.We included cluster randomised controlled trials. Participants were children and young people aged four to 18 years attending schools/colleges. HPS interventions had to include the following three elements: input into the curriculum; changes to the school’s ethos or environment; and engagement with families and/or local communities.Two reviewers identified relevant trials, extracted data and assessed risk of bias. We grouped studies according to the health topic(s) targeted. Where data permitted, we performed random-effects meta-analyses.ResultsWe identified 67 eligible trials tackling a range of health issues. Few studies included any academic/attendance outcomes. We found positive average intervention effects for: body mass index (BMI), physical activity, physical fitness, fruit and vegetable intake, tobacco use, and being bullied. Intervention effects were generally small. On average across studies, we found little evidence of effectiveness for zBMI (BMI, standardized for age and gender), and no evidence for fat intake, alcohol use, drug use, mental health, violence and bullying others. It was not possible to meta-analyse data on other health outcomes due to lack of data. Methodological limitations were identified including reliance on self-reported data, lack of long-term follow-up, and high attrition rates.ConclusionThis Cochrane review has found the WHO HPS framework is effective at improving some aspects of student health. The effects are small but potentially important at a population level.

Mathematics and Gender: Heterogeneity in Causes and Consequences

We exploit an institutional reduction in the costs of acquiring advanced high school mathematics to assess the causes and consequences of fewer girls choosing advanced mathematics. Girls at the top and boys at the middle of the mathematics ability distribution took more mathematics because of the cost reduction. We estimate a positive average earnings effect encompassing girls completing more advanced and more mathematics intensive college degrees, choosing more competitive careers and climbing higher up the corporate hierarchy. Encouraging more students to opt for advanced mathematics has a sizeable positive earnings effect for girls, but no effect for boys at the margin.

Going Beyond Late: Bounding Average Treatment Effects of Job Corps Training

We derive nonparametric sharp bounds on average treatment effects with an instrumental variable (IV) and use them to evaluate the effectiveness of the Job Corps (JC) training program for disadvantaged youth. We concentrate on the population average treatment effect (ATE) and the average treatment effect on the treated (ATT), which are parameters not point identified with an IV under heterogeneous treatment effects. The main assumptions employed to bound the ATE and ATT are monotonicity in the treatment of the average outcomes of specified subpopulations, and mean dominance assumptions across the potential outcomes of these subpopulations. Importantly, the direction of the mean dominance assumptions can be informed from data, and some of our bounds do not require an outcome with bounded support. We employ these bounds to assess the effectiveness of the JC program using data from a randomized social experiment with non-compliance (a common feature of social experiments). Our empirical results indicate that the effect of JC on eligible applicants (the target population) four years after randomization is to increase weekly earnings and employment by at least $24.61 and 4.3 percentage points, respectively, and to decrease yearly dependence on public welfare benefits by at least $84.29. Furthermore, the effect of JC on participants (the treated population) is to increase weekly earnings by between $28.67 and $43.47, increase employment by between 4.9 and 9.3 percentage points, and decrease public benefits received by between $108.72 and $140.29. Our results also point to positive average effects of JC on the labor market outcomes of those individuals who decide not to enroll in JC regardless of their treatment assignment (the so-called never takers), suggesting that these individuals would indeed benefit from participating in JC.

Social heuristics shape intuitive cooperation.

Cooperation is central to human societies. Yet relatively little is known about the cognitive underpinnings of cooperative decision making. Does cooperation require deliberate self-restraint? Or is spontaneous prosociality reined in by calculating self-interest? Here we present a theory of why (and for whom) intuition favors cooperation: cooperation is typically advantageous in everyday life, leading to the formation of generalized cooperative intuitions. Deliberation, by contrast, adjusts behaviour towards the optimum for a given situation. Thus, in one-shot anonymous interactions where selfishness is optimal, intuitive responses tend to be more cooperative than deliberative responses. We test this 'social heuristics hypothesis' by aggregating across every cooperation experiment using time pressure that we conducted over a 2-year period (15 studies and 6,910 decisions), as well as performing a novel time pressure experiment. Doing so demonstrates a positive average effect of time pressure on cooperation. We also find substantial variation in this effect, and show that this variation is partly explained by previous experience with one-shot lab experiments.

Effect of Microloans on the Livelihood of Beneficiaries: A Descriptive Study in Ethiopia

Microcredit has been found to be a critical instrument in order to improve the livelihood of the poor. It is prominently used to improve the livelihood of the household borrowers where it is believed to be under exploited in research. Hence, it is indispensable to examine its real effectiveness and to have sufficient information on the economic and social impact indicators (human capital). For the purpose of assessing the impact of DECSI microcredit on the livelihood of borrower households, a sample of 278 respondents (that is, 123 clients who had at least 3 years of attachment to the organization and 155 eligible non-participants representing the characteristics of the existing sample borrowers) was considered for the present study. Data were collected by using a semi-structured questionnaire that was prepared and distributed for both clients and eligible non-clients and the oral interviews were conducted while the questionnaires were filled out by the respondents. The results of the study revealed that microloan participation had a positive significant average effect on households' average monthly income, consumption expenditure, savings, and housing improvements. However, the number of employment opportunities generated for the household members showed not much of a difference. Whereas, the average effect on children's education and medical care expenditure was positive due to the respondents' participation in the microcredit program.

Efficacy of systemically oriented psychotherapies in the treatment of perinatal depression: a meta-analysis

The objective of this meta-analysis was to examine the efficacy of systemically oriented psychotherapy treatments for depression in pregnancy and the postpartum. Specifically, this synthesis examined standardized mean differences between pre- and posttest and treatment-control conditions in depression symptom reduction among 24 individual interpersonal psychotherapy or relational psychotherapy studies completed between 1997 and 2013. Analyses assessed heterogeneity, potential moderators, and publication bias. Random-effects analyses revealed a large, positive average effect size [Formula: see text] for psychotherapy treatments among one-group, pre-post-studies and a medium, positive average effect [Formula: see text] when treatments were compared with control groups. Mixed-effects meta-ANOVAs indicated that treatment type, participant depression severity, and method of depression assessment were significant moderators such that effect sizes were larger among individual interpersonal psychotherapy studies, clinical samples, and studies that included an independent evaluation of depression. However, relational treatments and studies with nonclinical samples were less represented in the literature, and still demonstrated small to medium positive effects. Meta-regressions revealed that effects were largest when treatments were delivered with adherence fidelity checks and over more sessions. Based on funnel plots and Egger tests, there was evidence of publication bias in this analysis; however, the effects were distributed fairly symmetrically about the mean given the relatively small number of available studies. Findings have implications for continued examination of systemically oriented psychotherapy treatments for depression in pregnancy and the postpartum.

Do SBA Loans Create Jobs? Estimates from Universal Panel Data and Longitudinal Matching Methods

Small Business Administration (SBA) loans have long been one of the most significant policy interventions in the U.S. affecting firm behavior, but little is known about their outcomes. This paper estimates the effects on employment using a list of all SBA loans linked to annual data on all U.S. employers from 1976 to 2010. Our methods combine firm fixed-effect regressions with matching on exact firm age, industry, year, and pre-loan size, and on propensity scores as a function of four years of employment history and other variables. The results imply positive average effects on loan recipient employment of about 25 percent, or 3 jobs at the mean. Including loan amount, we find little or no impact of loan receipt per se, but an increase of about 5.4 jobs for each million dollars of loans. Similar results for high-growth counties and industries suggest the estimates are not driven by differential demand conditions across firms. Exploiting variation in the distance of controls from recipient firms, we find only very small displacement effects. In all these cases, the results pass “placebo” and “pre-program” specification tests. Other specifications using only matching or only regression imply somewhat higher effects, but they fail these tests. The estimates facilitate calculations of total job creation by the SBA and of the cost per job created.

Math and Gender: Is Math a Route to a High-Powered Career?

We exploit an institutional reduction in the costs of acquiring advanced high school Mathematics to assess the causes and consequences of fewer girls choosing advanced Mathematics. Girls at the top and boys at the middle of the Mathematics-ability-distribution took more Mathematics because of the cost reduction. We estimate a positive average earnings effect for those who exogenously acquire more advanced Mathematics qualifications, where high Mathematics ability girls are pushed to the top and medium Mathematics ability boys are prevented from falling to the bottom of the earnings distribution. Marginal treatment effects reveal sizable positive earnings effects from encouraging even more girls to opt for advanced Mathematics, but insignificant earnings effects for boys at the margin. The earnings effect encompasses females completing more advanced and more Mathematics intensive college degrees, choosing more competitive careers, and to some extent climbing higher up the corporate hierarchy. Our results suggest that neither lack of Mathematics abilities nor labour market rewards discourage girls from taking advanced Mathematics courses. Instead it seems that access is deterred by too restrictive bundling of courses. This suggests there is a lost pool of Mathematics talent among high ability girls that may be accessed by changing the costs embedded in the educational environment and the institutional set-up of Mathematics teaching.

Do SBA Loans Create Jobs?

Small Business Administration (SBA) loans have long been one of the most significant policy interventions in the U.S. affecting firm behavior, but little is known about their outcomes. This paper estimates the effects on employment using a list of all SBA loans linked to annual data on all U.S. employers from 1976 to 2010. Our methods combine firm fixed-effect regressions with matching on exact firm age, industry, year, and pre-loan size, and on propensity scores as a function of four years of employment history and other variables. The results imply positive average effects on loan recipient employment of about 25 percent, or 3 jobs at the mean. Including loan amount, we find little or no impact of loan receipt per se, but an increase of about 5.4 jobs for each million dollars of loans. Similar results for high-growth counties and industries suggest the estimates are not driven by differential demand conditions across firms. Exploiting variation in the distance of controls from recipient firms, we find only very small displacement effects. In all these cases, the results pass placebo and pre-program specification tests. Other specifications using only matching or only regression imply somewhat higher effects, but they fail these tests. The estimates facilitate calculations of total job creation by the SBA and of the cost per job created.

Do SBA Loans Create Jobs? Estimates from Universal Panel Data and Longitudinal Matching Methods

This paper reports estimates of the effects of the Small Business Administration (SBA) 7(a) and 504 loan programs on employment. The database links a complete list of all SBA loans in these programs to universal data on all employers in the U.S. economy from 1976 to 2010. Our method is to estimate firm fixed effect regressions using matched control groups for the SBA loan recipients we have constructed by matching exactly on firm age, industry, year, and pre-loan size, plus kernel-based matching on propensity scores estimated as a function of four years of employment history and other variables. The results imply positive average effects on loan recipient employment of about 25 percent or 3 jobs at the mean. Including loan amount, we find little or no impact of loan receipt per se, but an increase of about 5.4 jobs for each million dollars of loans. Examining loans received only in high growth county-years (average growth of 22 percent), where most small firms should have excellent growth potential, we find similar effects, implying that the estimates are not driven by differential demand conditions across firms. Results are also similar regardless of distance of control from recipient firms, suggesting only a very small role for displacement effects. In all these cases, the results pass a “pre-program” specification test, where controls and treated firms look similar in the pre-loan period. Other specifications, such as those using only matching or only regression imply somewhat higher effects, but they fail the pre-program test.

Grading New York

This article uses a regression discontinuity approach to study the influence of New York City’s school grading policy on student math and English language arts (ELA) achievement. We find evidence that students in schools receiving a failing grade realized positive effects in English in the 1st year of sanction, but we find no statistically significant effect during the 1st year of sanction on student math achievement. There is no evidence that receiving letter grades other than F had positive effects. Finally, we show that students in schools that received an F-grade in the 1st year continued to realize a positive average ELA effect in the 2nd year and that a positive math effect was evident as well.

Reconciling the evidence of Card and Krueger (1994) and Neumark and Wascher (2000)

We employ the original Card and Krueger (American Economic Review 1994; 84: 772–793) and Neumark and Wascher (American Economic Review 2000; 90: 1362–1396) data together with the changes-in-changes estimator to re-examine the evidence for the effect of minimum wages on employment. Our study reconciles the controversial positive average employment effect reported by the former study and the negative average employment effect reported by the latter study. Our main finding, which is supported by both datasets, is that the controversial result remains valid only for small fast-food restaurants. Copyright © 2011 John Wiley & Sons, Ltd.

On the simultaneity problem in the aid and growth debate

SUMMARYThis paper shows that foreign aid has a significant positive average effect on real per capita gross domestic product (GDP) growth if, and only if, the quantitatively large negative reverse causal effect of per capita GDP growth on foreign aid is adjusted for in the growth regression. Instrumental variables estimates show that a 1 percentage point increase in GDP per capita growth decreased foreign aid by over 4%. Adjusting for this quantitatively large, negative reverse causal effect of economic growth on foreign aid shows that a 1% increase in foreign aid increased real per capita GDP growth by around 0.1 percentage points. Copyright © 2011 John Wiley & Sons, Ltd.