The article offers an overview of the use of survey experiments in political research by relying on available examples, bibliographic data and a content analysis of experimental manuscripts published in leading academic journals over the last two decades. After a short primer to the experimental approach, we discuss the development, applications and potential problems to internal and external validity in survey experimentation. The article also provides original examples, contrasting a traditional factorial and a more innovative conjoint design, to show how survey experiments can be used to test theory on relevant political topics. The main challenges and possibilities encountered in envisaging, planning and implementing survey experiments are examined. The article outlines the merits, limits and implications of the use of the experimental method in political research.

In the coronavirus disease 2019 (COVID-19) pandemic, a large number of non-pharmaceutical measures that pertain to the wider group of social distancing interventions (e.g. public gathering bans, closures of schools, workplaces and all but essential business, mandatory stay-at-home policies, travel restrictions, border closures and others) have been deployed. Their urgent deployment was defended with modelling and observational data of spurious credibility. There is major debate on whether these measures are effective and there is also uncertainty about the magnitude of the harms that these measures might induce. Given that there is equipoise for how, when and if specific social distancing interventions for COVID-19 should be applied and removed/modified during reopening, we argue that informative randomised-controlled trials are needed. Only a few such randomised trials have already been conducted, but the ones done to-date demonstrate that a randomised trials agenda is feasible. We discuss here issues of study design choice, selection of comparators (intervention and controls), choice of outcomes and additional considerations for the conduct of such trials. We also discuss and refute common counter-arguments against the conduct of such trials.

This paper reviews three UK-based welfare-to-work programmes featuring time-limited financial incentives to leave out-of-work benefits for employment. The policies considered are (i) the Employment Retention and Advancement demonstration, aimed at lone parents and the long-term unemployed; (ii) In-Work Credit, aimed at lone parents on welfare; (iii) Pathways to Work, aimed at recipients of incapacity benefits. I illustrate the difficulties in extrapolating from specific findings to general policy-relevant conclusions. Finally, I depict the challenge facing evaluators in future and point to the directions in which evaluation will need to develop if it is to contribute more fully to policy-relevant evaluation.

Statistical analysis of data collected in experimental or observational studies is an important part of nutritional research. If it is not done appropriately, there is a risk that information in the data is lost, or that conclusions are misleading. The present article does not attempt a full review of the subject of statistics, but attempts to list aspects where care is needed.