We show how to estimate a Cronbach's alpha reliability coefficient in Stata after running a principal component or factor analysis. Alpha evaluates to what extent items measure the same underlying content when the items are combined into a scale or used for latent variable. Stata allows for testing the reliability coefficient (alpha) of a scale only when all items receive homogenous weights. We present a user-written program that computes reliability coefficients when implementation of principal component or factor analysis shows heterogeneous item loadings. We use data on management practices from Bloom and Van Reenen (2010) to explain how to implement and interpret the adjusted internal consistency measure using afa.
Estimation of the factor model by unweighted least squares (ULS) is distribution free, yields consistent estimates, and is computationally fast if the Minimum Residuals (MinRes) algorithm is employed. MinRes algorithms produce a converging sequence of monotonically decreasing ULS function values. Various suggestions for algorithms of the MinRes type are made for confirmatory as well as for exploratory factor analysis. These suggestions include the implementation of inequality constraints and the prevention of Heywood cases. A simulation study, comparing the bootstrap standard deviations for the parameters with the standard errors from maximum likelihood, indicates that these are virtually equal when the score vectors are sampled from the normal distribution. Two empirical examples demonstrate the usefulness of constrained exploratory and confirmatory factor analysis by ULS used in conjunction with the bootstrap method.
A previous study found a variety of unusual sexual interests to cluster in a five-factor structure, namely submission/masochism, forbidden sexual activities, dominance / sadism, mysophilia, and fetishism (Schippers et al., 2021). The current study was an empirical replication to examine whether these findings generalized to a representative population sample. An online, anonymous sample (N = 256) representative of the Dutch adult male population rated 32 unusual sexual interests on a scale from 1 (very unappealing) to 7 (very appealing). An exploratory factor analysis assessed whether similar factors would emerge as in the original study. A subsequent confirmatory factor analysis served to confirm the factor structure. Four slightly different factors of sexual interest were found: extreme, illegal and mysophilic sexual activities; light BDSM without real pain or suffering; heavy BDSM that may include pain or suffering; and illegal but lower-sentenced and fetishistic sexual activities. The model fit was acceptable. The representative replication sample was more sexually conservative and showed less sexual engagement than the original convenience sample. On a fundamental level, sexual interest in light BDSM activities and extreme, forbidden, and mysophilic activities seem to be relatively separate constructs.
Since the 1970s, Caribbean reefs have transitioned from coral-dominated to algal-dominated ecosystems. The prevalence of algae reduces coral recruitment, rendering the reefs unable to recover from additional disturbances and jeopardizing crucial ecosystem services, including coastal protection, fisheries, and tourism. One of the main factors to the proliferation of algae is the scarcity of grazers, which is a result of overfishing and disease outbreaks. While fishing supports livelihoods, enhances local food security, and is an integral part of the Caribbean communities' culture, it remains a significant threat to coral reefs. Consequently, the Nature and Environmental Policy Plan (NEPP) 2020-2030, outlining conservation and restoration priorities in the Caribbean Netherlands, underscores the necessity of an integrated approach to tackle the complex challenges of coral reef restoration and fisheries development. The Saba government, and nature management organizations of Bonaire, St. Eustatius, and Saba are implementing the NEPP. Together with University of Applied Sciences Van Hall Larenstein, Wageningen University and WWF, they aim to identify novel species of native invertebrate grazers with the dual purpose of reef restoration and fisheries diversification. The Caribbean king crab (Maguimithrax spinosissimus), the West Indian sea egg (Tripneustes ventricosus), and the West Indian top shell (Cittarium pica) have been identified as potential candidates. Despite their preference to graze on macroalgae, their current densities are inadequate. Population enhancement of these species holds promise for reducing algae, promoting biodiversity, and simultaneously supporting small-scale fisheries. However, there is limited knowledge regarding the ecological effects and socio-economic potential of these grazers. The ReefGrazers project aims to assess the current densities of these herbivores around the BES islands, analyze their impacts on the reef, and evaluate their retention post-restocking. Socio-economic research will quantify current small-scale fishing practices, while market analysis will help assess the potential for the development of these novel resources as sustainable fisheries.
