1157 search results for "latex"

Checking for Normality with Quantile Ranges and the Standard Deviation

Checking for Normality with Quantile Ranges and the Standard Deviation

Introduction I was reading Michael Trosset’s “An Introduction to Statistical Inference and Its Applications with R”, and I learned a basic but interesting fact about the normal distribution’s interquartile range and standard deviation that I had not learned before.  This turns out to be a good way to check for normality in a data set.

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Benford law and lognormal distributions

March 28, 2013
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Benford law and lognormal distributions

Benford’s law is nowadays extremely popular (see e.g. http://en.wikipedia.org/…). It is usually claimed that, for a given set data set, changing units does not affect the distribution of the first digit. Thus, it should be related to scale invariant distributions. Heuristically, scale (or unit) invariance means that the density of the measure  (or probability function) should be proportional to...

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Rationality, and MS Excel (and other calculators)

March 27, 2013
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Rationality, and MS Excel (and other calculators)

This morning, Mathieu had a nice experience in his course on computational method in actuarial science. But let us start with some mathematical formal definitions. First, recall that is – somehow – a standard expression. No one should be surprised to see such an expression. Generally (as explained in http://en.wikipedia.org/… ), this function is defined only when . The...

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Model assessment (and predictions for RuPaul’s Drag Race Season 5, Episode 9)

March 25, 2013
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Model assessment (and predictions for RuPaul’s Drag Race Season 5, Episode 9)

Last week, Alaska took it home with her dangerous performance, while Ivy Winters was sent home after going up against Alyssa Edwards. This is sad on many fronts. First, I love me some Ivy Winters. Second, Jinkx had revealed that she had a crush on Ivy, and the relationship that may have flourished between the… Continue reading →

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Writing a MS-Word document using R (with as little overhead as possible)

March 24, 2013
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Writing a MS-Word document using R (with as little overhead as possible)

The problem: producing a Word (.docx) file of a statistical report created in R, with as little overhead as possible. The solution: combining R+knitr+rmarkdown+pander+pandoc (it is easier than it is spelled). If you get what this post is about, just …Read more »

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Estimating the Decay Rate and the Half-Life of DDT in Trout – Applying Simple Linear Regression with Logarithmic Transformation

Estimating the Decay Rate and the Half-Life of DDT in Trout – Applying Simple Linear Regression with Logarithmic Transformation

This blog post uses a function and a script written in R that were displayed in an earlier blog post. Introduction This is the second of a series of blog posts about simple linear regression; the first was written recently on some conceptual nuances and subtleties about this model.  In this blog post, I will use

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Veterinary Epidemiologic Research: GLM – Evaluating Logistic Regression Models (part 3)

March 19, 2013
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Veterinary Epidemiologic Research: GLM – Evaluating Logistic Regression Models (part 3)

Third part on logistic regression (first here, second here). Two steps in assessing the fit of the model: first is to determine if the model fits using summary measures of goodness of fit or by assessing the predictive ability of the model; second is to deterime if there’s any observations that do not fit the

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One Pager Performance Report with knitr, R, and a Different Font

March 18, 2013
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Although I suffer from complete ignorance of typography, with a little help from a post from Hyndsight and post from mages' blog, I wanted to try a different font on the one-pager performance report that we created in Onepager Now with knitR. I do not think Open Sans Light is the best choice for this...

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Veterinary Epidemiologic Research: GLM – Logistic Regression (part 2)

March 17, 2013
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Veterinary Epidemiologic Research: GLM – Logistic Regression (part 2)

Second part on logistic regression (first one here). We used in the previous post a likelihood ratio test to compare a full and null model. The same can be done to compare a full and nested model to test the contribution of any subset of parameters: Interpretation of coefficients Note: Dohoo do not report the

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Veterinary Epidemiologic Research: GLM – Logistic Regression

March 14, 2013
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Veterinary Epidemiologic Research: GLM – Logistic Regression

We continue to explore the book Veterinary Epidemiologic Research and today we’ll have a look at generalized linear models (GLM), specifically the logistic regression (chapter 16). In veterinary epidemiology, often the outcome is dichotomous (yes/no), representing the presence or absence of disease or mortality. We code 1 for the presence of the outcome and 0

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