Recent examples for such situations include the controversy surrounding a possible association between intramuscular administration of vitamin K to newborns and the risk of childhood cancer 8 and whether oral contraceptives increase women's risk of breast cancer. 9 Summary points Meta-analysis of observational studies is as common as meta-analysis of controlled trials Confounding and selection bias often distort the findings from observational studies There is a danger that meta-analyses of observational data produce very precise but equally spurious results The statistical combination of data should therefore not be a prominent component of reviews of observational studies More is gained by carefully examining possible sources of heterogeneity between the results from observational studies Reviews of any type of research and data should use a systematic approach, which is documented in a materials and methods section The patients who are enrolled in randomised trials often differ from the average patient seen in clinical practice. 34 The meta-analysis of exposure to sunlight and risk of melanoma was exceptional in its thorough examination of possible reasons for heterogeneity, and the calculation of a combined estimate was deemed appropriate in one subgroup of population based studies only. 37 Conversely, uninformative and potentially misleading combined estimates were calculated both in the study on dietary calcium and blood pressure 38 and in the meta-analysis of occupational exposure to formaldehyde. 41 These case studies show that the temptation to combine the results of studies seems to be hard to resist.
Ionic channels are proteins with holes down their middle that control access to biological cells and thus govern an enormous range of biological functions important in health and disease. A substantial fraction of the drugs used in clinical medicine act directly or indirectly on channels. Channels have a simple well-defined structure, and the fundamental mechanism of ionic motion is known to be electrodiffusion. The current through individual channel molecules can easily be measured, and is in fact measured in hundreds if not thousands of laboratories everyday. Thus, ionic channels are ideal objects for physical investigation: on the one hand, they are well-defined structures following simple physics, on the other hand they are of general biological importance. A simple theory of ion permeation through a channel is presented, in which diffusion occurs according to Fick's law and drift according to Ohm's law, in the electric field determined by all the charges present. This theory accounts for permeation in the channels studied to date in a wide range of solutions. Interestingly, the theory works because the shape of the electric field is a sensitive function of experimental conditions, e.g. ion concentration. Rate constants for flux are sensitive functions of ionic concentration because the fixed charge of the channel protein is shielded by the ions in and near it. Such shielding effects are not included in traditional theories of ionic channels, or other proteins, for that matter.
Researchers typically analyze time-series-cross-section data with a binary dependent variable (BTSCS) using ordinary legit or probit. However, BTSCS observations are likely to violate the independence assumption of the ordinary legit or probit statistical model. It is well known that if the observations are temporally related that the results of an ordinary legit or probit analysis may be misleading. In this paper, we provide a simple diagnostic for temporal dependence and a simple remedy. Our remedy is based on the idea that BTSCS data are identical to grouped duration data. This remedy does not require the BTSCS analyst to acquire any further methodological skills, and it can be easily implemented in any standard statistical software package. While our approach is suitable for any type of BTSCS data, we provide examples and applications from the field of International Relations, where BTSCS data are frequently used. We use our methodology to reassess Oneal and Russett's (1997) findings regarding the relationship between economic interdependence, democracy, and peace. Our analyses show that (1) their finding that economic interdependence is associated with peace is an artifact of their failure to account for temporal dependence yet (2) their finding that democracy inhibits conflict is upheld even taking duration dependence into account.
In this paper I explore the questions of why and how sociologists should be interested in narrative. The answer to the first question is straightforward: Narrative texts are packed with sociological information, and a great deal of our empirical evidence is in narrative form. In an attempt to answer the second question, I look at definitions of narrative, distinguishing narrative from non-narrative texts. I highlight the linguistic properties of narrative and illustrate modes of analysis, paying close attention to both the structural properties of the text and its subtle linguistic nuances. I guide the reader through a detailed analysis of a short narrative text. I show how linguistics and sociology interplay at the level of a text.