Tag Archives: statistics

Confused interactions

I am used to confused interactions, likely because I get along better with dogs and kids than I do with adults. But that is not what Nieuwenhuis et al. had in mind when they surveyed 513 articles relating to behavior, cognitive function or brain imaging from leading journals (Nature, Science, Nature Neuroscience, Neuron, Journal of Neurosience). What they were looking

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Understanding interaction (subgroup) analysis in randomised studies

When we try to interpret findings from a study, we often like to understand whether an effect (of a treatment or test condition) might be different in subjects with different characteristics. If there was substantial variability among subjects, this may have masked a treatment effect in a select few. How can we understand effects in select groups of subjects that

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Why we need to report more than “Data were analysed by t-tests or ANOVA”

T-tests and analysis of variance (ANOVA) are common statistical tests in physiology and biomedical science. While the SAMPL guidelines for reporting statistical analyses and methods in published literature state authors should “describe statistical methods with enough detail to enable a knowledgeable reader with access to the original data to verify the reported results”, such recommendations are rarely implemented. Simply stating

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Research concepts: Confidence interval of a mean

In previous posts, we learned that the aim of statistics is to extrapolate properties of samples to make inferences about population. However, random variation in individuals in the population produces sampling error, which means a single sample may not accurately reflect properties of the population. When data are binary, we learned how the 95% confidence interval (CI) of a sample

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Research concepts: The Normal Distribution

At Scientifically Sound, we have shown how to verify whether data are Normally distributed, and discussed whether it matters that data are Normally distributed. Let’s take a step back and consider what a Normal distribution is. A Normal distribution is a bell-shaped curve observed when the number of data points that occur in a population (y-axis) is plotted against the

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Research concepts: Quantifying scatter

In a previous post we used binary data to demonstrate sampling error and calculate 95% confidence intervals (CI). Now, suppose that data can take many values; for example, normal body temperature has many values and varies continuously over a physiological range. How can we measure this variability in body temperature? For continuous data, variability can be quantified as the standard

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