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Public Health Workforce Training
Link to beginning section of Advanced Program Evaluation

Randomized Controlled Trials

ShapeTracker Intervention Stakeholders

  • Commissioner Middleton County (MC)
  • Middleton County (MC) Health Department (HD) ShapeTracker (ST) team
  • MC HD Information Technology staff
  • MC HD marketing/communications staff
  • Other MC HD staff
  • CDC
  • Group that developed ST for CDC
  • MC community members
  • Wellness advocates in MC
  • Obesity prevention programs in MC
  • Healthy eating related resources in MC
  • Exercise resources in MC
  • Smartphone providers in MC
  • California communities that implemented ST
  • Smartphone companies
  • MC government

Logic Model

Inputs Activities Outputs Short-term Outcomes Intermediate Outcomes Long-term Outcomes
ShapeTracker App Mobilize local resources and customize ST for MC # of times ST app downloaded in MC Decrease perceived barriers to healthy eating and physical activity Increase healthy eating in MC Reduce obesity in MC
Funding from HD and CDC Market ST in MC # of MC residents actively using ST Increase self-monitoring of healthy eating and physical activity Increase physical activity in MC Reduce obesity related health problems in MC
Team of experienced staff Keep app updated and maintain content Amount of use for different ST functions Increase self-efficacy for healthy eating and physical activity    
High smart phone use in MC community Provide technical assistance to users User satisfaction with ST Increase social supprt for healthy eating and physical activity    
Marketing & communication resources in HD   # of friends referred to ST      
IT resources in HD   # of MC residents actively using ST long-term      
Local obesity prevention resources in MC          

ShapeTracker Intervention Evaluation Questions

Process Questions
  1. Was a broad range of local resources successfully engaged in the project?
  2. Was ST successfully disseminated to a broad segment of MC community?
  3. What proportion of MC residents have:
    • downloaded the app?
    • became active users of the app?
    • became active long-term users of the app?
  4. For those who stopped using ST, why did they discontinue?
  5. How much are ST users using different functions in ST?
  6. How satisfied are MC residents with the ST app and its specific features?
Outcome Questions
  1. Does use of ST increase:
    • self-monitoring of healthy eating and physical activity?
    • self-efficacy for healthy eating and physical activity?
    • social support for healthy eating and physical activity?
  2. Does ST decrease perceived barriers to healthy eating and physical activity?
  3. Does use of ST increase healthy eating and physical activity among county residents?
  4. Does use of ST lead to lower BMI among those who are obese or overweight?
  5. Does use of ST help those with normal BMI prevent overweight?

The evaluation questions we have chosen to address in our evaluation plan.

Let’s start with the most rigorous option and consider whether a randomized design with a control group is possible for our study. In such a design, there must be a way to randomly assign a pool of participants into two groups. One of the groups will then be exposed to the intervention, in our case, the ShapeTracker. If we find a difference between the groups, we can be fairly certain that the difference was caused by our intervention, and not by some other difference between the two groups.

You may have seen the following notation used to specify the components of a randomized design:

R
O
X
O
R
O
 
O

The two rows represent the two groups. The Rs indicate that the groups are randomly assigned. The Os indicate when outcomes are measured. In this case, both groups provide a baseline measure and a post-test. Note that only the first group has an X, which means that they are exposed to the intervention.

Is it possible to have randomly assigned groups in our ShapeTracker evaluation? For the questions below, determine if the following scenarios would give us a randomized controlled design by selecting “Yes” or “No.”

Question 1:

Implement and disseminate ShapeTracker only in the western half of the county. Compare a randomly selected sample of ShapeTracker users in western Middeton county with a sample of non-users with similar sociodemographic characteristics living in the eastern half of the county.

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The correct answer is B:
There is no randomized assignment. Note that random selection is about sampling and does not mean random assignment. But the group of non-users in eastern Middleton could be a comparison group in a quasi-experimental design.

Question 2:

Add ShapeTracker questions to the annual representative county household survey. Compare those who report using ShapeTracker to those who report not using ShapeTracker.

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The correct answer is B:
Again, there is no randomized assignment because there is no control group. But those who report not using ShapeTracker could be defined as a comparison group, especially if we try to control for sociodemographic and other group characteristics in the statistical analysis.

Question 3:

As people request their ShapeTracker user ID, every other person is placed on a wait-list. The waitlisted group will have to wait one year to get access to ShapeTracker.

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The correct answer is A:
This would give us randomly assigned groups. A systematic method of random assignment is defined. However, this plan may not be feasible if we think people will resent being waitlisted. Also, we would have to consider if “contamination” of the control group is possible. For example, maybe those with access to ShapeTracker will share some of the benefits with the control group members who might be their family members of neighbors.