Assessing the

construct validity of

food environment

measures: A multitrait-

multimethod matrix

approach

Leia Minaker, PhD (cand) Kim Raine, PhD Cam Wild, PhD

Candace Nykiforuk, PhD Larry Frank, PhD

Outline

Background

Food environment measures

Construct validity

Why a Multitrait Multimethod Matrix?

Methods

Results

Conclusions

Food Environment: Conceptual Model

Construct Validity

The extent to which a measure assesses the trait it purports to measure, and behaves consistently with theoretical hypotheses

Operational definition: How are constructs measured?

Syntactical definition: How are constructs related to one another in a theoretical system?

Three Constructs/Traits

Food availability

Food affordability

Food quality

Multitrait-Multimethod Matrix

Methods: NEWPATH

NEWPATH study

2397 Households

Food environment perceptions from the

head of each household

4-point Likert scale assessed agreement with

statements related to neighbourhood food

environments along constructs of food

availability (3 statements); food affordability

(3 statements); food quality (2 statements)

Methods: Objective Food

Environment Measures

N=422 stores, including grocery stores, specialty stores, pharmacies, superstores, and convenience stores in 3 cities

NEMS-S: Comprehensive inventory assessing food availability, food affordability and food quality

Shelf-Space: Linear shelf space (m) of fruits and vegetables, assesses food availability

Retail Food Environment Index (RFEI): ratio of number of fast-food outlets and convenience stores to grocery and specialty stores, assesses food availability

Methods: Procedure

Euclidean distance buffer zones were

established around NEWPATH

participants’ households at 250m, 500m,

1000m and 1500m.

Household-level variables for each

method-trait combination were

created(e.g., NEMS-S affordability;

Perceived affordability, etc.)

MTMM-Matrices were created for each

buffer zone size (N=4)

NEMS-S Shelf-

Space

RFEI Perceptions

A B C A A A B C

NEMS-S

A. Availability 0.86

B. Quality 0.43 0.93

C. Affordability -0.27 -0.23 -0.17

Shelf-Space

A. Availability 0.31 -0.01 0.02 >0.86

RFEI

A. Availability 0.03 -0.08 -0.25 0.19

Perceptions

A. Availability 0.17 0.04 -0.03 0.26 0.04 0.75

B. Quality 0.17 0.04 -0.07 0.21 0.03 0.83 0.83

C. Affordability -0.01 -0.11 0.03 -0.001 0.06 -0.17 -0.11 0.77

Walkability 0.00 -0.07 0.21 0.58 0.21 0.16 0.10 0.05

MTMM: Convergent validity Variables Correlation:

250m

Correlation:

500m

Correlation:

1000m

Correlation

: 1500m

Food availability

NEMS & Shelf Space 0.911 0.849 0.455 0.174

NEMS & RFEI 0.851 0.724 0.213 0.069

NEMS & Perceptions -0.010 0.036 0.213 0.069

Shelf Space & RFEI 0.789 0.798 0.343 -0.019

Shelf Space & Perceptions 0.014 0.081 0.262 0.238

RFEI & Perceptions 0.005 0.020 0.035 0.007

Food Quality

NEMS & Perceptions -0.045 -0.032 0.035 -0.030

Food Affordability

NEMS & Perceptions 0.022 0.013 0.029 0.036

Conclusions

Choice of measurement tool has to be carefully considered, since they don’t all do the same job and in fact may not be measuring the same constructs (low convergent validity)

Choice of geographic scale has implications for construct validity

Future studies should examine which food environment measures best predict diet-related outcomes(syntactic definition) in the context of restricted resources

Acknowledgements Stipend support to Leia Minaker funded by the Heart and Stroke Foundation of Canada and the CIHR Training Grant in Population Intervention for Chronic Disease Prevention: A Pan-Canadian Program (Grant #53893). Leia Minaker also received a CIHR Banting and Best Doctoral Award and an AIHS PhD Studentship award during the research process.