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When to Use Different Inferential Methods for Power Analysis and Data Analysis for Between-Subjects Mediation
Several options exist for conducting inference on indirect effects in mediation analysis. Although methods that use bootstrapping are the preferred inferential approach for testing mediation, they are time-consuming when the test must be performed many times for a power analysis. Alternatives that are more computationally efficient are not as robust, meaning accuracy of the inferences from these methods is more affected by nonnormal and heteroskedastic data. Previous research has shown that different sample sizes are needed to achieve the same amount of statistical power for different inferential approaches with data that meet all the statistical assumptions of linear regression. By contrast, we explore how similar power estimates are at the same sample size, including when assumptions are violated. We compare the power estimates from six inferential methods for between-subjects mediation using a Monte Carlo simulation study. We varied the path coefficients, inferential methods for the indirect effect, and degree to which assumptions are met. We found that when the assumptions of linear regression are met, three inferential methods consistently perform similarly: the joint significance test, the Monte Carlo confidence interval, and the percentile bootstrap confidence interval. When the assumptions were violated, the nonbootstrapping methods tended to have vastly different power estimates compared with the bootstrapping methods. On the basis of these results, we recommend using the more computationally efficient joint significance test for power analysis only when no assumption violations are hypothesized a priori. We also recommend the joint significance test to pick an optimal starting sample size value for power analysis using the percentile bootstrap confidence interval when assumption violations are suspected
Cyt‐Geist: Current and Future Challenges in Cytometry: Reports of the CYTO 2019 Conference Workshops
The need for cytometry instrumentation, reagents, training and scientific collaborations in the nations of Africa remains high despite strong efforts by both the African and foreign biomedical and cytometry research communities. Dr. Tesfa and Dr. Blanco therefore organized the first Cytometry in Africa Workshop at CYTO2019. This workshop had several goals. The first goal was to present the results of a pre-workshop survey aimed at assessing flow cytometry resources, personnel, experience and training in Africa. The results of this survey demonstrated important strengths in the African cytometry community, but also pinpointed areas where instrument access, reagent availability and training could be improved. The second goal was to present several collaborative scientific projects in Africa with participation by ISAC members. Third, both existing and proposed strategies for improving collaborative efforts and research support were presented, including cytometer donations, research collaborations and training programs. Finally, an open roundtable discussion was held with workshop attendees, many with experience in working in Africa. A diverse array of investigators from government, academia and industry attended and contributed to the workshop. A key outcome of the workshop was the establishment an African Working group in collaboration with the ISAC Instruments 4 Science Task Force, the ISAC Live Education Task Force, and the ISAC Education Committee. The workshop also marked the establishment of I4S, with the goal of advancing flow cytometry in the international research communit