Using Case Summaries in SPSS to Debug your Variable Creation

Here’s a little SPSS tip.

When you create new variables, whether it’s through the Recode, Compute, or some other command, you need to check that it worked the way you think it did.

(As an aside, I hope this goes without saying, but never, never, never, never use Recode into Same Variable. Always Recode into New Variable so you

Read the full article →

R Tutorial Series

I actually wish R had been around, and I wish all the great resources for learning it that exist now, existed then.

Here’s one of them. A very lovely-looking R tutorial series by John M. Quick.

Read the full article →

How to do a Chi-square test when you only have proportions and denominators

How do you then do a cross-tabulation in SPSS when you do not have a dataset with the values of the two variables of interest? For example, if you do a critical appraisal of a published study and only have proportions and denominators. In this article it will be demonstrated how SPSS can come up with a cross table and do a Chi-square test in both situations. And you will see that the results are exactly the same.

Read the full article →

Recoding Variables in SPSS Menus and Syntax

If you don’t have many variables to recode, say one or two, it’s not a big deal to use the menus (but at least paste the code, so you have a record of what you did later!).

But if you have more than just one or two, all those mouse-clicks get old, fast.

Read the full article →

Approaches to Repeated Measures Data: Repeated Measures ANOVA, Marginal, and Mixed Models

In a marginal model, we can directly estimate the correlations among each individual’s residuals. (We do assume the residuals across different individuals are independent of each other). We can specify that they are equally correlated, as in the RM ANOVA, but we’re not limited to that assumption. Each correlation can be unique, or measurements closer in time can have higher correlations than those farther away. There are a number of common patterns that the residuals tend to take.

Read the full article →

R code for the Random Intercept and Random Slope Models Webinar

If you’ve ever run Mixed models, you know that correctly specifying in your statistical software the model you think you’re specifying is half the battle.

As I usually do, I demonstrated an example in the webinar using SPSS. And I made the data available in .csv format for anyone who wanted to try it out in the software of their choosing.

Read the full article →

Mixed Models for Logistic Regression in SPSS

Can I use SPSS MIXED models for (a) ordinal logistic regression, and (b) multi-nomial logistic regression?

Every once in a while I get emailed a question that I think others will find helpful. This is definitely one of them.

My answer:

Read the full article →

The Difference Between Clustered, Longitudinal, and Repeated Measures Data

In repeated measures data, the dependent variable is measured more than once for each subject. Usually, there is some independent variable (often called a within-subject factor) that changes with each measurement.

And in longitudinal data, the dependent variable is measured at several time points for each subject, often over a relatively long period of time.

Read the full article →

Grant Proposal Writing: A Great Resource

But you also have to change the focus of the writing. According to Dr. Morgan Giddings, a biologist-turned-grant writing consulant, one of the three deadly mistakes researchers make in writing grant proposals is writing them the same way you would write a research article. The audience is different, the purpose is different, and the way you write it has to be different.

Read the full article →

Poisson and Negative Binomial Regression for Count Data

Ever discover that your data are not normally distributed, no matter what transformation you try? It may be that they follow another distribution altogether. Although they are numerical, discrete count data often follow a Poisson or Negative Binomial distribution, not a normal one. Examples of discrete counts include: Number of tagged fish that return to [...]

Read the full article →

← Previous Entries

Next Entries →