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At some point, we've all likely heard the cautionary assertion that correlation is not causation. It sounds reasonable so we tend to accept the assertion, but what does it really mean? And is it always true?To answer these questions, we first need to understand what the terms mean and how they are distinguished from one another. Correlation is a mathematical representation that summarizes the measured association between variables. In simpler terms, it's a number between -1 and 1 that describes what happens to one variable (let's call this variable y) when another variable changes (let's call this one x). Causation takes correlation a bit further by demanding more from our variables than a basic association. Causation requires that at least part of the the change we see in variable y is actually due to changes in variable x. In other words, a change in one variable has actually caused a change in the other, hence the term causal.First, let's look at how correlations between variables can be misleading. The scatterplot in Fig. 1 shows simulated data from a sample of 50 elementary students, grades 1-6. The plot shows two variables for each student: a measure of shoe size along the x-axis (var.x) and performance on a common math test along the y-axis (var.y). Each point in the plot represents the intersection between those variables for each student in our simulated sample. The association between these variables is clear, as shoe size (x) increases, so do our math scores (y). There is a rather wide range in math scores across shoe sizes, but this range doesn't throw off the overall association demonstrated by the linear increase indicated by the blue line of best fit. To further reinforce this association, we can look at the calculated correlation statistic between shoe size and math performance [r(xy)=.74]. [If this statistic is unfamiliar, see Linear Association and Correlation.] This is a strong correlation, certainly something to take notice of, and provides further evidence for the association between shoe size and math performance within our sample.

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LaTeX is a powerful free and open-source academic writing system; however, it does come with a learning curve. This curve can be especially steep when trying to incorporate bibliographic references and formatting a document to the current writing style of the field - APA 6th edition. Anyone who has submitted a manuscript for publication is familiar with the trials and tribulations of formatting and citing sources. Any tool to help with this process is a welcome one. Although LaTeX comes close to APA compatibility natively, it doesn't quite nail it. This post describes how to set-up and integrate a powerful (and free) LaTeX editor with a powerful (and free) citation manager to assist with formatting and citing. To get started, you will need to download and install two programs. Texmaker: LaTeX editorZotero: citation managerThen download two files that will run on these programs.APA 6th File: LaTeX document formatting codeBetter BibTex: program for generating cite keysThese programs and files are compatible with the major operating systems. Installation with Windows and macOS is largely a matter of point and click. Installation on Linux requires a bit more know-how of course; and it's assumed that those using a Linux distribution are familiar with the processes for installing programs and various file extensions. If you are already familiar with the terminology of LaTeX and citation managers then read on. If not, it would be helpful to first review the key terms listed at the end of this post. Zotero Set-upZotero can be used separately as a reference manager, but its real utility comes from its ability to generate a bibliographic reference file (i.e., .bib file) that contains cite keys for each of your references. These cite keys are entered into a LaTeX document to generate citations. Although Zotero has a great deal of native functionality, some set-up is required for fluid integration with LaTeX. First, you need to install Better BibTex, a program for generating those cite keys.From the Zotero toolbar, navigate to: Tools > Add-ons > Extensions.Select the gear icon in the top-right corner and select ‘Install Add-on From File…’ Navigate to the folder where you saved the Better Bibtex file and install it. At this point you will need to restart Zotero to complete the install and auto-update to the most recent version of Better Bibtex. Navigate back to Extensions and make sure Better Bibtex is now listed. You may see an option for preferences. Don't worry about setting-up the Better BibTex preferences yet; that will be done in a moment.