Presentation of the Groningen group plan

Marijtje van DuijnECRP Meeting

Ljubljana, Feb. 2, 2012

Who is (who?) in Groningen

• Marijtje van Duijn• Christian Steglich• Christophe Stadtfeld

• Tom Snijders• Mark Huisman• Filip Agneessens• …

What do we do – for ECRP?

• Statistics, models, methods, simulation/computing, applications …

• ECRP project: Peer Influence in Social Networks: Comparing and Evaluating Methods across Domains.

• Focused on influence – and disentangling it from selection (contagion vs. homophily)

Influence vs. selection

• Hot topic!• Requirements– Longitudinal data– Adequate statistical model/method

• SAOM; network autocorrelation; GEE; SEM; …

• Why difficult? (interesting!)– Results seem to depend on model used– Adequacy of model assumptions

• Not straightforward in longitudinal social network data• No ‘independent’ observations …

• Lots of debate

The Groningen contribution

Comparing and evaluating method• Two dimensions

1. Models (used for the analysis)2. Data (and their properties)

• SAOM (RSiena) is the starting/reference point– Analysis– Data generation

• Simulation studies– Aimed at comparison of models/methods

General purpose of a simulation study

• Show that (estimation) method works well• Generate data according to model• Estimate model parameters• Show that these are ‘good’ (unbiased, etc.)

• Show that model estimation is sensitive to assumption violation and/or misspecification

• Generate ‘wrong’ data• Use ‘wrong’ model for estimation• Evaluate estimation resuls

Rough design of ECRP simulation study

• Generate data and analyze it with – the ‘true’ model and – other ‘wrong’ models– Compare the results of both analyses

• Works for SAOM (can do both)• More difficult for other models/methods

– E.g. GEE has implicit way of controlling for dependence in the network data• How use it for data generation? What are true parameter values?

– What are realistic parameter choices, i.e. leading to plausible network data (structures)

Input from/output to other projects

• Other projects may provide interesting and realistic data configurations – For our data generating

• Our methods may be useful for other projects– Advice for choosing analysis method– For analysis of your data

• Great for collaboration!

Why now (and not earlier)?

• Interesting question…• Some possible answers– Focus on model development (as a start)– Various approaches to model development

(different groups; working on similar problems; with different modeling solutions)

– Now that models have been developed, a wider view is possible

– …???

First start

• Christoph’s presentation tomorrow

• Questions and suggestions …???