255 search results for "anova"

Power and Sample Size Analysis: Z test

October 17, 2012
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Power and Sample Size Analysis: Z test

This article provide a brief background about power and sample size analysis. Then, power and sample size analysis is computed for the Z test. Continue reading →

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Color Palettes in HCL Space

October 12, 2012
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Color Palettes in HCL Space

This is a quick follow-up to my previous post about Color Palettes in RGB Space. Achim Zeileis had commented that, perhaps, it would be more informative to evaluate the color palettes in HCL (polar LUV) space, as that spectrum more accurately describes how humans perceive color. Perhaps more clear trends would emerge in HCL space,

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Product revenue prediction with R – part 2

October 8, 2012
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Product revenue prediction with R – part 2

After development of predictive model for transactional product revenue -(Product revenue prediction with R – part 1), we can further improvise the model prediction by modifications in the model. In this post, we will see what are the steps required for model improvement. With the help of a set of model summary parameters, the data

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Two ways that correlation and stepwise regression can give different results

October 8, 2012
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In general, a correlation test is used to test the association between two variables (y and z). However, if there is a third variable (x) that might be related to z or y, it makes...

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Parse pdf files with R (on a Mac)

October 4, 2012
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Inspired by this blog post from theBioBucket, I created a script to parse all pdf files in a directory. Due to its reliance on the Terminal, it’s Mac specific, but modifications for other systems shouldn’t be too hard (as a start for Windows, see BioBucket’s script). First, you have to install the command line tool

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R 2.15.2 scheduled for October 26

October 2, 2012
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The next minor update to R — version 2.15.2 "Trick or Treat" — will be released on October 26, R-core member Peter Dalgaard announced today. You can find the planned updates in the current NEWS file (scroll down to the section 'CHANGES IN R VERSION 2.15.1 patched'; the changes at the top of the file are planned for the...

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Football, an ordinal model

September 30, 2012
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Football, an ordinal model

On September 19th, flo2speak remarked under a post that his/her experience is that ordinal models had better performance. That seems reason enough to try, so there we are. In examining this type of model it is found that more complex models can be...

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Power Analysis and the Probability of Errors

September 22, 2012
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Power Analysis and the Probability of Errors

Power analysis is a very useful tool to estimate the statistical power from a study. It effectively allows a researcher to determine the needed sample size in order to obtained the required statistical power. Clients often ask (and rightfully so) what the sample size should be for a proposed project. Sample sizes end up being

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Some helps for running and evaluating Bayesian regression models

September 21, 2012
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Around two years ago, I suddenly realized my statistical training had a great big Bayes-shaped hole in it. My formal education in statistics was pretty narrow – I got my degree in anthropology, a discipline not exactly known for its rigorously systematic analytic methods. I learned the basics of linear models and principal components analysis

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Football model

September 16, 2012
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Football model

After reading Dutch football data (Eeredivisie 2011-2012) and making a predictions display it is time to look at a few simple models to predict goals. To reiterate the data setup, each game played consists of two rows in the data frame. ...

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