CALIFORNIA STATE UNIVERSITY LONG BEACH
PPA 696--RESEARCH METHODS:
BINGHAM & FELBINGER CH. 11
  1. BIBLIOGRAPHIC INFORMATION
    1. Author: P. K. Edwards, A. C. Acock & R. L. Johnston
    1. Title: Nutritional Behavior Change: Outcomes of an Educational Approach
    1. Source: Evaluation Review, 9(4), 1985:441-459

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  1. SUMMARY OF THE RESEARCH
    1. PROBLEM STATEMENT:
There is a need for effective nutrition programs targeted to help broad audiences sustain changes over time
    1. BACKGROUND:
There is a lack of reliable and valid measures of nutritional attitudes, knowledge, and practices for longitudinal assessment of the general public
    1. HYPOTHESIS:
Participation in a nutrition program will improve attitudes, knowledge, and practices over the short and long term
    1. MEASUREMENT OF VARIABLES
      1. Dependent variable: 1) nutrition knowledge; 2) nutrition beliefs; 3) nutrition practices
      1. Independent variable(s): Nutrition program
      1. Control variable(s): gender; race; age; education; income
    1. RESEARCH DESIGN:
A non-experimental design, using a single group pre- and post-test design (see comments about "comparison group" below).
Group Time 1 Program Time 21 Time 3
G-1 O1 X O2 O3
 
    1. SAMPLING:
Participants were self-selected volunteers; telephone survey included program completers and program drop-outs
    1. INSTRUMENTATION:
Three scales were developed and tested to measure nutritional 1) knowledge; 2) belief; and 3) behavior. Reliability of the scales was low to moderate (.56 to .82). However, scales were condensed for the telephone survey, which lessened their reliability.
    1. DATA COLLECTION/ETHICS:
Data were collected by questionnaires at the first and last program meetings, and then by telephone survey 10 weeks after course completion.
    1. DATA ANALYSIS:
Alpha coefficient used to test for reliability of scales; two-tailed t-tests were used to compare pre- and post-program scale scores for participants and for telephone survey participants.
    1. CONCLUSIONS:
The program was able to improve nutritional knowledge, beliefs, and behavior scores over the short run for program completers. Scores declined over the long run but did not fall below baseline (pre-program) levels.
  1. CRITIQUE
    1. Possible Threats to Internal Validity
      1. History:
No control for history over the program or post-program period
      1. Maturation:
No control for maturation, but little probability of effect
      1. Testing:
Scores on post-test and follow-up could have been influenced by taking the pre-test
      1. Instrumentation:
Instrument used for the pre- and post-test was changed for the 10-week follow up so results are not strictly comparable
      1. Regression Artifact:
People could have enrolled in the program based on extremely low scores, and could have improved over time regardless
      1. Selection bias:
People enrolled in the program were volunteers; those who completed the program were self-selected and could have different motivation than those who dropped out. Researchers report a "control group" but it does not provide a meaningful control.
      1. Experimental Mortality:
1461 people began the program, and 1031 completed it, for a drop out rate of 29%. Only 200 follow-up telephone interviews were completed, and not all were program completers.
      1. Design contamination:
n/a
    1. Possible Threats to External Validity
      1. unique program features:
Program features could be widely applied
      1. experimental arrangements:
Not different from usual nutrition classes
      1. other threats: