Increased quantification of scientific research and a prolifera- tion of large, complex datasets in recent years have expanded the scope of applications of statistical methods. This has created new avenues for scientific progress, but it also brings concerns about conclusions drawn from research data. The validity of scientific conclusions, including their reproducibility, depends on more than the statistical methods themselves. Appropriately chosen techniques, properly conducted analyses and correct interpre- tation of statistical results also play a key role in ensuring that conclusions are sound and that uncertainty surrounding them is represented properly. Underpinning many published scientific conclusions is the concept of “statistical significance,” typically assessed with an index called the p-value. While the p-value can be a use- ful statistical measure, it is commonly misused and misinter- preted. This has led to some scientific journals discouraging the use of p-values, and some scientists and statisticians recom- a proposed context is a m tions, togethe the null hypo such as no diff of a relations smaller the p bility of the d ing assumptio incompatibili or providing underlying as 2. P-values do n ied hypothes were produc Researche ment about t probability th data. The p-v rah Mayo, Michele Millar, Charles Poole, Ken Rothman, Stephen Senn, Dalene Stangl, Philip Stark and Steve Ziliak for sharing their insightful perspectives. Of special note is the following article, which is a significant contribution to the literature about p-values and statistical significance. Greenland, S., Senn, S.J., Rothman, K.J., Carlin, J.B., Poole, C., Good- man, S.N. and Altman, D.G.: “Statistical Tests, P-values, Confidence Intervals, and Power: A Guide to Misinterpretations.” Though there was disagreement on exactly what the state- ment should say, there was high agreement that the ASA should be speaking out about these matters. Let us be clear. Nothing in the ASA statement is new. Statisti- cians and others have been sounding the alarm about these mat- ters for decades, to little avail. We hoped that a statement from the world’s largest professional association of statisticians would open a fresh discussion and draw renewed and vigorous atten- tion to changing the practice of science with regards to the use of statistical inference. P- r Li r M wi r M tio r Ro ca r Se r St r St r Zi sta Refere America Lim polic Gelman, [onl n - t m e n - g - y ) - s e h - ing assumptions used to calculate the p-value hold. This incompatibility can be interpreted as casting doubt on or providing evidence against the null hypothesis or the underlying assumptions. 2. P-values do not measure the probability that the stud- ied hypothesis is true, or the probability that the data were produced by random chance alone. Researchers often wish to turn a p-value into a state- ment about the truth of a null hypothesis, or about the probability that random chance produced the observed data. The p-value is neither. It is a statement about data in relation to a specified hypothetical explanation, and is not a statement about the explanation itself. 3. Scientific conclusions and business or policy decisions should not be based only on whether a p-value passes a specific threshold. Practices that reduce data analysis or scientific infer- ence to mechanical “bright-line” rules (such as “p < 0.05”) for justifying scientific claims or conclusions can were produced by random chance alone. Researchers often wish to turn a p-value into a state- ment about the truth of a null hypothesis, or about the probability that random chance produced the observed data. The p-value is neither. It is a statement about data in relation to a specified hypothetical explanation, and is not a statement about the explanation itself. 3. Scientific conclusions and business or policy decisions should not be based only on whether a p-value passes a specific threshold. Practices that reduce data analysis or scientific infer- ence to mechanical “bright-line” rules (such as “p < 0.05”) for justifying scientific claims or conclusions can lead to erroneous beliefs and poor decision making. A conclusion does not immediately become “true” on one side of the divide and “false” on the other. Researchers should bring many contextual factors into play to derive scientific inferences, including the design of a study,
Social Research Structural Causal Models Directed acyclic graphs (DAGs) Partially directed acyclic graphs (PDAGs) 265 b Dj (t+1) Uj Hj Dj (t+1) Mi,j Mi,j Di (t) Ui Hi Di (t) ial network analysis is endogenous selection bias. Mij , marital status of woman i and man stics inﬂuencing marital choice and vital status; H, health in old age. (a) Computing the implies conditioning on Mij , which induces an association between Di and Dj even if D (b) If Di affects Dj only if i and j are married (effect modiﬁcation), then the existence o n the DAG, Di !Dj and Mij !Dj . Conditioning on either one of Hi or Hj would block the nditioning on the social tie Mij and allow for the identiﬁcation of the causal effect of D
grandparental investment: a journey towards causality David A Coalla,b, Sonja Hilbrandc,d, Rebecca Seare and Ralph Hertwigd aSchool of Medical and Health Sciences, Edith Cowan University, Joondalup, WA, Australia;bDivision of Psychiatry, School of Medicine, University of Western Australia, Crawley, WA, Australia;cDepartment of Psychology, University of Basel, Basel, Switzerland;dCenter for Adaptive Rationality, Max Planck Institute for Human Development, Berlin, Germany;eDepartment of Population Health, London School of Hygiene and Tropical Medicine, London, UK ABSTRACT Why do grandparents invest so heavily in their grandchildren and what impact does this investment have on families? A multitude of factors influence the roles grandparents play in their families. Here, we present an interdisciplinary perspective of grandparenting incorporating theory and research from evolutionary biology, sociology and economics. Discriminative grandparental solicitude, biological relatedness and the impact of resource availability are three phenomena used to illustrate how these perspectives, within such a multi-level approach, add value by complementing not competing with each other. Changing demographics mean there is greater demand and opportunity for ARTICLE HISTORY Received 15 November 2017 Accepted 23 January 2018 KEYWORDS Grandparents; interdisciplinary perspectives; grandparent health; grandparental investment; grandchild development CONTEMPORARY SOCIAL SCIENCE, 2018 https://doi.org/10.1080/21582041.2018.1433317
covariate is added to model • Purely statistical phenomenon • Uninterpretable without a causal model P G (Intercept) -0.5 0.0 0.5 1.0 1.5 Value child ~ grandparent + parent
V. Pollet & Joshua M. Tybur & Willem E. Frankenhuis & Ian J. Rickard Published online: 5 August 2014 # Springer Science+Business Media New York 2014 Abstract Many recent evolutionary psychology and human behavioral ecology studies have tested hypotheses by examining correlations between variables measured at a group level (e.g., state, country, continent). In such analyses, variables collected for each aggregation are often taken to be representative of the individuals present within them, and relationships between such variables are presumed to reflect individual-level processes. There are multiple reasons to exercise caution when doing so, including: (1) the ecological fallacy, whereby relationships observed at the aggregate level do not accurately represent individual-level processes; (2) non-independence of data points, which violates assumptions of the inferential techniques used in null hypothesis testing; and (3) cross-cultural non-equivalence of measurement (differences in construct valid- ity between groups). We provide examples of how each of these gives rise to problems (e.g., Marlowe et al. 2008, 2011), and sexual dimorphism (Wells 20 Fig. 1 Three levels at which hypotheses can be analyzed: between groups, betw groups, and within individuals over time. Note: Interactions between levels might exi if the differences between individuals, or the developmental trajectories of individuals Re-evaluating the link between brain size and behavioural ecology in primates Lauren E. Powell1, Karin Isler2 and Robert A. Barton1 1
direct influence on daughter (Y) • X and Y confounded by common U • Birth order (B) reduces mom’s RS (X) X U Y B Code at https://gist.github.com/rmcelreath