Day 63: The Train: A framework to organize research

Somehow, I managed to achieve one of my biggest goals of this year in June: I defended my dissertation proposal. I spent almost three years working towards this point. I thought I would never reach this milestone. I had nightmares about being kicked out because I was taking too long. I thought that living in …

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Endogeniety

Endogeniety simply means that a parameter or variable is correlated with the error term. There are many reasons why this would happen: Measurement error This happens when we do not have an accurate measure of the independent variables. Omitted variables This happens when the model does not include all the variables it should, and thus …

Fixed vs. Random Effects

The best way to think about the difference between random and fixed effects is with this picture. Fixed effects can be thought of as the relationship between predictor and outcome within an entity. In addition: Assumes something about entity may bias predictor/outcome so need to control for it Removes effects of observed or unobserved time-invariant …

Structural Equation Modeling

When you think that there are unobserved or latent variables, a potential technique is Structural Equation Modeling (SEM). Among other advantages, SEM: Can control for random errors Can model measurement error so the model is more precise Can test elaborate models In general, the SEM starts by looking at all of the relationships in your …

Survival Analysis

Survival analysis is used when we need to choose a point in time to measure survival, success, failure, death, etc.. Two important concepts relate to the time that we observe the data. This is referred to as censoring and it comes in two varieties: left and right. Left censoring happens when we do not know …

Categorical DVs

When the DVs are categorical variables, different analyses should be used. The most common (and the only one discussed in class) is the case of a binary outcome variable. If this is the case either Logit or Probit should be used. Logistic regression estimates the probability of the outcome variable having a certain value (as …

Moderators and Mediators

A moderator is a qualitative or quantitative variable that affects the direction and/or strength of the relation between an IV (or predictor) and a dependent or criterion variable. Within a correlational analysis framework, a moderator is a third variable that affects the zero-order correlation between two other variable. In the more familiar ANOVA terms, a …

Analysis of Variance and Sundry

Here I will write very briefly about some analysis. T-Test This test compares the means to two groups. The goal is to determine if they are statistically different from one another. Analysis of Variance These include the MANOVA, ANOVA and MANCOVA and ANCOVA. The MANOVA test compares the multivariate means of multiple groups. If this …

Factor Analysis

The first steps to take with new data were already discussed in the previous post. Factor analysis comes in two varieties: Exploratory and Confirmatory: Exploratory factor analysis is used when you don't have a clear idea of what items might belong together. There are many ways to see what items belong together. The principal component …

Research Methods

The research methods section will consist of several short posts. In each entry, I will discuss the general ideas behind each technique. I do not intend on detailing how to perform each technique. The general process for dealing with a dataset is as follows: The first step is to understand the data: Check for missing …