Wednesday, November 22, 2017

Why is Incidence Rate Important?

Simply put, it directly affects how much it will cost to complete the desired number of surveys in a study. The higher the incidence rate, the easier it is to complete surveys with qualified respondents. This translates into lower data collection and study costs.

What Exactly is Incidence Rate?

There is no one answer to this as incidence can be measured several different ways. From a theoretical perspective, the incidence rate is the frequency of something occurring in a given population. If 20% of all households in the U.S. have a color laser printer at home, for instance, then the Theoretical Incidence Rate (T.I.R) of color laser printers in households is 20%. In a market research study that uses a purely random sampling technique (such as random digit dialing – RDD), we would need to contact five households on average to find one with a color laser printer.

From a practical standpoint, market research firms are interested in knowing bottom line what percentage of people contacted will actually qualify and complete the survey. TechWise refers to this as the Actual Incidence Rate (AIR). It can be (and usually is) very different from the Theoretical Incidence Rate. The characteristics of the list used in the study, along with the screening criteria and survey design all impact A.I.R. For instance, a list of registered color laser printer owners will have a higher incidence rate than a random list of households. Let's assume that a study requires that all people surveyed purchased their color laser printer from an office supply store. There are many different ways of purchasing color laser printers. If the customer list does not identify where the printer was purchased, this screening requirement will make it harder to find qualified respondents (which translates into a lower A.I.R.). Finally, let's assume that the final survey lasts 20 minutes. Some qualified respondents will refuse upfront to spend that much time on a survey while others will drop out in the middle of the study. Drop outs decrease a study's A.I.R.

Actual Incidence Rate (AIR) Calculator

Below are the definitions for the terms used in this calculator.

  • Completes: Completed interviews
  • Not Qualified: Respondents who are disqualified because they do not meet one or more of the screening criteria.
  • Over Quota: Respondents who would have been considered eligible if it were not for their quota group being full. A quota is an artificial limit that is placed on certain types of respondents.
  • Refused: These are respondents who refuse to participate in the survey.
  • Drop Outs: Respondents who end the interview prematurely after having been successfully qualified.
  • Bad Contacts: Contact records in the list that are inaccurate. Examples include disconnected or wrong telephone number for phone surveys and undeliverable or incorrect email addresses for web surveys.
To use, enter the number of completes (must be greater than 0), change any of the other entries as needed, then click "Calculate." Note: all fields are required. Enter 0 if none.

 

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