A Review of ‘A Step-by-Step Approach to Using SAS for Factor Analysis and Structural Equation

Modeling’ (Larry Hatcher)

By Barry DeCicco, September 23, 2010

B. DeCicco, MSUG, 23 Sep 10 2

Do I recommend this book?

• Yes - if you are looking to start performing factor analyses and structural equations modeling (SEM) in SAS, and you do not have extensive experience in other statistics packages, especially if your math/stats background is weak.

• No - if you are familiar with factor analysis/SEM in other packages, then you can probably go to the SAS/STAT user’s guide, and learn the new syntax (see ‘other resources’ slide near the end).

B. DeCicco, MSUG, 23 Sep 10 3

What this book is NOT

• A matrix algebra explanation of factor analysis and structural equation modeling (SEM).

B. DeCicco, MSUG, 23 Sep 10 4

What this book IS

• A light regression explanation of factor analysis and SEM.

• A guide on how to perform that in SAS, what the goals are and how to interpret the results.

• (in the appendices) an introduction to how to do things in SAS.

• Approachable with a low level of statistical background.

B. DeCicco, MSUG, 23 Sep 10 5

Outline of this book• Principle component analysis (looking for combinations of

observed variables).• Factor analysis (looking for latent variables which explain

observed variables).• Scale reliability (a short chapter, need-to-know material only).• Path analysis – manifest (observed) variables only.• Measurement models/CFA (linking manifest with latent variables

to evaluate measurement quality). • Structural equation analysis – manifest variables measuring

latent variables which are linked to each other; this book also covers model-fitting.

• Appendices on how to use SAS, write programs, enter data, and handle output.

B. DeCicco, MSUG, 23 Sep 10 6

What needs supplementing

• Fit indices – they cover a variety of fit indices and helpfully list them by portion of the model being tested (pg 391), but this field is rapidly evolving.

• ODS – this is a pre-ODS book, and I found ODS extremely helpful in getting output into useable form (e.g., into Excel).

B. DeCicco, MSUG, 23 Sep 10 7

What I liked

• Extremely step-by-step.• Good explanation on how to estimate

reliabilities of latent variables. I was able to estimate reliabilities and ‘true’ correlations of latent factors, comparing them to a more naïve approach.

B. DeCicco, MSUG, 23 Sep 10 8

Comment on SAS Syntax

• With SEM, Proc Calis requires multiple long lists of linear equations.

• Using Excel formulae to write them out saves a lot of time:

B. DeCicco, MSUG, 23 Sep 10 9

Comment: SAS vs. AMOS• I worked on learning Proc CALIS (the classic SEM

procedure for SAS) with this book at the same time I was learning AMOS, which is the SPSS SEM package.

• AMOS has a graphical user interface.• This is great; one can draw models, and AMOS can

automatically fill in multiple items.• Sometimes AMOS’s ‘help’ isn’t so helpful.• I was surprised that it was frequently no harder to

do things in SAS than in a GUI-driven program.

B. DeCicco, MSUG, 23 Sep 10 10

The Sweet Side of AMOS

0, 1

Hospital Environment

0, 1

Nursing

Nurseslisten

0,

e1

Nrsng court,resp

0,

e2

1

1

0, 1

Doctor

Doctorsexplain

0,

e3

Doctorslisten

0,

e4

Doctors courtesy,respect

0,

e5

1

1

1

0, 1

OutcomesRate

0,

e6

Recommend

0,

e7

1

1

Nursesexplain

0,

e81

Noise

0,

e91

Roomclean

0,

e101

0, 1

Hospital Experience

Help toileting

0,

e111

Pain cntrl

0,

e121

Staff help w/pain

0,

e131

Explainnew med

0,

e141

Describe medside effect

0,

e151

Call button

0,

e161

B. DeCicco, MSUG, 23 Sep 10 11

The Sour Side of AMOS

0,

Admission

a1

0,

e11

1a2

0,

e21

0,

Discharge

d1

0,

e31

1d2

0,

e41

d3

0,

e51

0,

Visitors

v2

0,

e61

1

v3

0,

e71

0,

Meals

m2

0,

e81

1m3

0,

e91

m4

0,

e101

0,

Doctor

p1

0,

e11

11p2

0,

e121p3

0,

e131p4

0,

e141p5

0,

e151

0,

Tests_treatments

t1

0,

e16

1

1

t3

0,

e171

t5

0,

e181

t7

0,

e191

0,

Room

r1

0,

e201

1

r2

0,

e211

r3

0,

e221

r4

0,

e231

r5

0,

e241

0,

Inconvenience

i60,

e25

1

1i50,

e261i40,

e271i3 0,

e281i10,

e291

0,

Nursing

n1

0,

e30

1

1

n2

0,

e311

n3

0,

e321

n4

0,

e331

n5

0,

e341

n6

0,

e351

0, 1

Outcomes

o20,

e36

1

1o30,

e371o40,

e381

B. DeCicco, MSUG, 23 Sep 10 12

Other resources for this topic• ‘A Handbook of Statistical Analyses with SAS’ has a chapter on factor

analysis; nothing on SEM.• SAS Help documents ‘The FACTOR Procedure’, ‘Introduction to

Structural Equation Modeling with Latent Variables‘ and ‘The CALIS Procedure’ cover the syntax, and have very condensed introductions to the material.

• http://www.ats.ucla.edu/stat/sas/default.htm has a very large body of very well done work on how to use SAS, and how to run statistical analyses.

• Statnotes: Topics in Multivariate Analysis, by G. David Garson (http://faculty.chass.ncsu.edu/garson/PA765/statnote.htm) The best site on the internet for people who find themselves needing to do a lot of graduate-level statistics, without the graduate degree in statistics. It generally assumes the use of SPSS, but the concepts translate.

B. DeCicco, MSUG, 23 Sep 10 13

Where to get this presentation

• Go to the Ann Arbor ASA website: https://sites.google.com/site/annarborasa/

• Choose ‘Presentations and Class Materials’ on the left-hand menu: https://sites.google.com/site/annarborasa/A2ASA/presentations-and-class-materials

• Look for the folder ‘September 2010 MSUG Presentation’. This presentation and any associated documents will be there.