Heterogeneous heterogeneity by default: Testing categorical moderators in mixed-effects meta-analysis

Categorical moderators are often included in mixed-effects meta-analysis to explain heterogeneity in effect sizes. An assumption in tests of categorical moderator effects is that of a constant between-study variance across all levels of the moderator. Although it rarely receives serious thought, there can be statistical ramifications to upholding this assumption. We propose that researchers should instead default to assuming unequal between-study variances when analysing categorical moderators. To achieve this, we suggest using a mixed-effects location-scale model (MELSM) to allow group-specific estimates for the between-study variance. In two extensive simulation studies, we show that in terms of Type I error and statistical power, little is lost by using the MELSM for moderator tests, but there can be serious costs when an equal variance mixed-effects model (MEM) is used. Most notably, in scenarios with balanced sample sizes or equal between-study variance, the Type I error and power rates are nearly identical between the MEM and the MELSM. On the other hand, with imbalanced sample sizes and unequal variances, the Type I error rate under the MEM can be grossly inflated or overly conservative, whereas the MELSM does comparatively well in controlling the Type I error across the majority of cases. A notable exception where the MELSM did not clearly outperform the MEM was in the case of few studies (e.g., 5). With respect to power, the MELSM had similar or higher power than the MEM in conditions where the latter produced non-inflated Type 1 error rates. Together, our results support the idea that assuming unequal between-study variances is preferred as a default strategy when testing categorical moderators.     

Principles of Discipleship and Church Growth from Acts 2:46-47

The purpose of this article is to make a comprehensive exegesis of the text of Acts 2:46-47 and to extract basic biblical principles for the work of discipleship. Along with this topic, this article also analyzes the aspect of the growth of the church, since the study text indicates that the Lord added new converts to the church, although the church itself had an internal task to fulfil. Even though church growth has generally been distanced from doctrinal catechesis in the church in the same way that theology is divorced from ecclesiastical practice, this work attempts to show that a responsible and simple exegesis of the text can integrate the “theory” of doctrine with missionary practice and the responsibility to make disciples, so that the church increases in membership.     

Contingency tracking during unsignaled delayed reinforcement

Three experiments were conducted with rats in which responses on one lever (labeled the functional lever) produced reinforcers after an unsignaled delay period that reset with each response during the delay. Responses on a second, nonfunctional, lever did not initiate delays, but, in the first and third experiments, such responses during the last 10 s of a delay did postpone food delivery another 10 s. In the first experiment, the location of the two levers was reversed several times. Responding generally was higher on the functional lever, though the magnitude of the difference diminished with successive reversals. In the second experiment, once a delay was initiated by a response on the functional lever, in different conditions responses on the nonfunctional lever either had no effect or postponed food delivery by 30 s. The latter contingency typically lowered response rates on the nonfunctional lever. In the first two experiments, both the functional and nonfunctional levers were identical except for their location; in the third experiment, initially, a vertically mounted, pole-push lever defined the functional response and a horizontally mounted lever defined the nonfunctional response. Higher response rates occurred on the functional lever. These results taken together suggest that responding generally tracked the response-reinforcer contingency. The results further show how nonfunctional-operanda responses are controlled by a prior history of direct reinforcement of such responses, by the temporal delay between such responses and food delivery, and as simple generalization between the two operanda.     

Research Participants’ Preferences for Hypothetical Secondary Results from Genomic Research

Secondary or incidental results can be identified in genomic research that increasingly uses whole exome/genome sequencing. Understanding research participants’ preferences for secondary results and what influences these decisions is important for patient education, counseling, and consent, and for the development of policies regarding return of secondary results. Two hundred nineteen research participants enrolled in genomic studies were surveyed regarding hypothetical preferences for specific types of secondary results, and these preferences were correlated with demographic information and psychosocial data. The majority of research participants (73%) indicated a preference to learn about all results offered, with no clear pattern regarding which results were not desired by the remaining participants. Participants who reported greater interest in genetic privacy were less likely to indicate a preference to learn all results, as were individuals who self-identified as Jewish. Although most research participants preferred to receive all secondary results offered, a significant subset preferred to exclude some results, suggesting that an all-or-none policy would not be ideal for all participants. The correlations between preferences to receive secondary results, religious identification, and privacy concerns demonstrate the need for culturally sensitive counseling and educational materials accessible to all education levels to allow participants to make the best choices for themselves.     

Searching for Evidence of Transfer between Drug Facilitators

Four autoshaping experiments with pigeons examined the transfer of facilitation between drug stimuli. In Experiment 1 the presence and absence of methadone or phencyclidine signaled which of two keylight CSs were followed by grain (US). A different keylight CS was reinforced in the absence of the drugs. The drugs facilitated responding to the CS with which they were trained but did not facilitate responding to the CS reinforced in the presence of the other drug. Thus, transfer of facilitation across drug stimuli was not obtained. In Experiment 2 one of the drug facilitators was replaced by a tone. No evidence of transfer of facilitative function was obtained between the tone and the remaining drug facilitator. In Experiment 3 transfer was again not found using a design similar to that used in Experiment 1 except that the drugs did not simultaneously signal nonreinforcement of a keylight CS. In Experiment 4 the procedures of Experiment 1 were employed except that drug facilitators were replaced by distinct visual stimuli surrounding the response key. Clear evidence of transfer between the visual facilitators was obtained. The lack of transfer of modulatory control by drug stimuli in Experiments 1-3, coupled with its occurrence in Experiment 4 and previous studies, suggests that stimulus control by drugs may differ in important ways from stimulus control by conventional stimuli.     

HIV-positive pregnant women attending the prevention of mother-to-child transmission of HIV/AIDS (PMTCT) services in Ethiopia: economic productivity losses across urban-rural settings

HIV/AIDS impacts significantly on pregnant women and on children in Ethiopia. This impact has a multiplier effect on household economies and on productivity losses, and is expected to vary across rural and urban settings. Applying the human capital approach to data collected from 131 respondents, this study estimated productivity losses per HIV-positive pregnant woman–infant pair across urban and rural health facilities in Ethiopia, which in turn were used to estimate the national productivity loss. The study found that the annual productivity loss per woman–infant pair was Ethiopian birr (ETB) 7,433 or United States dollar (US$) 378 and ETB 625 (US$ 32) in urban and rural settings, respectively. The mean patient days lost per year due to inpatient admission at hospitals/health centres was 11 in urban and 22 in rural health facilities. On average, urban home care-givers spent 20 (SD = 21) days annually providing home care services, while their rural counterparts spent 23 days (SD = 26). The productivity loss accounted for 16% and 7% of household income in urban and rural settings, respectively. These high and varying productivity losses require preventive interventions that are appropriate to each setting to ensure the welfare of women and children in Ethiopia.