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Multicolinearity: Why you should care an...

Multicolinearity: Why you should care and what to do about it Multicolinearity is a problem for statistical analyses. This large, unwieldy word essentially refers to situations where your predictor variables so highly correlated with one another, they become redundant. Generally speaking, this is a problem because it will increase your Type II error rate (i.e., false negatives). In the most severe cases, multicolinearity can produce really bizarre results that defy logic. For example, the direction of relationships can sometimes reverse (e.g., a positive relationship...
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Growth Curves Tutorial

In 2013, I was invited by the IWK to give a short workshop on growth curves using SPSS software. I’ve since published the slides online using SlideShare for anyone to use as materials for learning or teaching. Check them out here:
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Single Imputation using the Expectation-Maximization Algorithm

Single Imputation using the Expectation-...

In this post, I outline when and how to use single imputation using an expectation-maximization algorithm in SPSS to deal with missing data. I start with a step-by-step tutorial on how to do this in SPSS, and finish with a discussion of some of the finer points of doing this analysis. 1. Open the data-file you want to work with. 2. Sort the data file by ascending ID or Participant number. This is critical; if you do not do this, everything you do subsequently could be inaccurate. To do this, right click on the ID column, and click “sort ascending” 3. Open the Syntax...
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Four Simple SPSS Syntax Tips

Four Simple SPSS Syntax Tips

Here are four useful tips for writing shorter, more efficient SPSS syntax. 1. A simpler way to calculate scale totals. I often need to calculate a total score for questionnaires with multiple items. For example, I might ask participants to answer ten different questions, responding to each question using a scale of 1 (strongly disagree) to 5 (strongly agree). In particular, I’ll often want to calculate an average of all ten items to use in statistical analyses. I used to calculate scale totals using the following SPSS syntax: COMPUTE vartotal = (var1 + var2 + var3 + var4...
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Converting an SPSS datafile to Mplus format

Converting an SPSS datafile to Mplus for...

Converting an SPSS datafile into a format readable by Mplus Mplus  is a fabulous statistical program. It’s very flexible, and is my favorite program to use when I need to analyze data using structural equation modeling – and I definitely prefer it over AMOS software. The latter is easier to use because of the graphical user interface (GUI), but I often find myself running into software limitations (e.g., AMOS cannot use bootstrapping when there is missing data) and in complex models, I often find the GUI tends to get clunky, and visually cluttered. This said, Mplus is not...