## Statistical Horizons Blog

#### Imputation by Predictive Mean Matching: Promise & Peril

Predictive mean matching (PMM) is an attractive way to do multiple imputation for missing data, especially for imputing quantitative variables that are not normally distributed. But, as I explain below, it’s also easy to do it the wrong way.  Compared with standard methods based on linear regression and the normal distribution, PMM produces imputed values […]

#### Getting the Lags Right

In my November and December posts, I extolled the virtues of SEM for estimating dynamic panel models. By combining fixed effects with lagged values of the predictor variables, I argued that this approach offers the best option for making causal inferences with non-experimental panel data. It controls for all time-invariant variables, whether observed or not, […]

#### More on Causal Inference With Panel Data

This is a follow-up to last month’s post, in which I considered the use of panel data to answer questions about causal ordering: does x cause y or does y cause x?  In the interim, I’ve done many more simulations to compare the two competing methods, Arellano-Bond and ML-SEM, and I’m going to report some […]

#### Using Panel Data to Infer Causal Direction: ML vs. Arellano-Bond

Does x cause y or does y cause x? Virtually everyone agrees that cross-sectional data are of no use in answering this question. The ideal, of course, would be to do two randomized experiments, one examining the effect of x on y, and the other focused on the reverse effect. Absent this, most social scientists […]

#### Sensitivity Analysis for Not Missing at Random

When I teach my seminar on Missing Data, the most common question I get is “What can I do if my data are not missing at random?” My usual answer is “Not much,” followed by “but you can do a sensitivity analysis.” Everyone agrees that a sensitivity analysis is essential for investigating possible violations of […]

#### Problems with the Hybrid Method

For several years now, I’ve been promoting something I called the “hybrid method” as a way of analyzing longitudinal and other forms of clustered data. My books Fixed Effects Regression Methods for Longitudinal Data Using SAS (2005) and Fixed Effects Regression Models (2009) both devoted quite a few pages to this methodology. However, recent research […]

#### Free SAS!

UPDATE, 11 February 2021.  SAS University Edition will soon be phased out.  It will end completely on Aug. 2, 2021. You will no longer be able to download it after Apr. 30, 2021. It’s being replaced by SAS OnDemand for Academics, which is now available here. The user experience is very similar, but there are […]

#### Prediction vs. Causation in Regression Analysis

In the first chapter of my 1999 book Multiple Regression, I wrote “There are two main uses of multiple regression: prediction and causal analysis. In a prediction study, the goal is to develop a formula for making predictions about the dependent variable, based on the observed values of the independent variables….In a causal analysis, the […]