Reach
(Extent of Representativeness of Participants)
In designing your study, consider purposeful sampling
from diverse groups of participants (e.g. low-income, older adults,
and racially-diverse) to enhance external validity.
Consider recruitment methods and intervention features
that enhance the reach within populations of persons and settings.
Carefully review exclusion criteria and consider whether
by excluding certain types of participants you are also decreasing
ability to generalize results.
Estimating Reach and Recruitment of Individuals
- Based on the available literature, your experience, and with
formative evaluation, try to anticipate the primary barriers
to participation of your program. How can you minimize or introduce
methods to address these barriers in order to enhance participation?
- Estimate the number and percentage of people in your local population
that have the targeted risk factor of interest. (e.g., number
and % of smokers, sedentary adults, post-myocardial infarction
cases)*
- Estimate the approximate percent of this targeted population
that will be eligible due to specific study inclusion/exclusionary
criteria. (e.g., of all adult hypertensives, what percent are
excluded due to medication, other diseases, language barriers)*
- Record the actual number and percent of persons excluded from
your study.
- Report the percent of eligible participants who agree to participate
in your study.
- Compare differences between those participating and those not
participating on illness status, sociodemographics, geography
and other key variables.
- Record reasons that participants refused to participate in the
study.
Estimating Attrition
Do the following for each study condition:
- Record how many ____ and when (what week of the intervention)
_____ subjects dropped from the study.
- Compare differences between those completing and those not completing
the study on adverse events, illness status, sociodemographics,
geography, baseline scores on dependent variables, and other
key variables.
