• How do I calculate reach if denominator (target population) is unknown?
• How do I calculate adoption if the number of potentially eligible settings is unknown?
• What variables should I use to determine the representativeness of the organizations involved in my program?

How do I calculate Reach when our "denominator" or target population is not known?

There are several ways of estimating Reach, and there are some websites listed on our Links page that may be of help. It is often possible to use either census data, data from national representative surveys such as NHANES or the CDC BRFSS, or information available from public agencies or marketing organizations that will allow you to estimate the number of eligible persons in a given geographic area. Two important guidelines to remember are to report the exclusion rate for your study (as well as exclusion criteria) and to state specifically if you drew your sample from some exhaustive list (such as all patients in a health plan, all students in the school); or if your initial list of potential participants were interested volunteers (such as those responding to an advertisement or self-selecting to participate)

See also Calculating and Reporting Reach

Click here to read a list of suggestions for estimating target populations or "Reach denominators." (It will open a new window.)

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How do I calculate Adoption if the population of potentially eligible settings is not known?

There are several ways of estimating Adoption rates, and some websites listed below that may be of help. It is often possible to use either census data, data from national surveys, professional associations (e.g., of businesses, schools, churches, employers), chambers of commerce, state licensing bureaus, marketing organizations or even phone books that will allow you to estimate the number of eligible organizations or settings in a given geographic area. Two important guidelines to remember are to report the exclusion rate for your study (as well as exclusion criteria) and to state specifically if you drew your sample from some exhaustive list versus approached those settings that you judged to be best able to implement your protocol or most interested.

See also Adoption Calculator

What types of variables should I use to determine the representativeness of the organizations involved in my program (and those who decline)?

This depends on what is known about organizational characteristics that are related to outcomes in the particular area you are studying. A fairly common list of issues to consider would include: size of organization; history and stability of the organization; number of full-time versus part time staff; if the organization is unionized; history of health promotion; relevant health policies; whether time off work is provided for participation in such activities; percent of members or employees by gender; race and ethnicity, level of education, and job title. Of course, not all of this information will be available in every case. Often information can be collected over the phone from a personnel or human resources representative, or from standard sources described above in the section on Adoption.

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