Data Collection ECPS surveys are administered using an Interactive Voice Response (IVR) system (straticsnetworks.com). By eliminating the live human interviewer, the IVR system reduce interviewer bias to zero and every respondent hears the exact same message in either English or Spanish. The system data is entered directly into a computerized database through the numbers on interviewee’s phone, providing a highly reliable system of data collection. Sampling Method A random sample of registered voters or all citizens depending on the needs of the survey are purchased from Aristotle Inc., a leading supplier of phone lists to the survey research industry. It has been demonstrated that random list of phone numbers are more accurate for political purposes than random digit dialing.
Through the use of a screening question, we usually seek out "likely voters" which has been shown to give a much more representative sample of the populations for most political polling. Data Analysis The results presented in our reports include univariate and bivariate analysis of the data. Frequency distributions for each item included on the questionnaire are shown in tables. In all cases, cross-tabulation results are also shown. This type of bivariate analysis examines differences between sub-groups of the overall population.
Weighting To achieve a representative sample we employ a weighting technique of demographic breakdowns.
Our first step in weighting is to survey more than enough people. This allows us to then be able to systematically reject individual surveys from demographics that are over represented. Next, survey data is weighted with a 3 point decrease in Conservative opinion and a 3 point increase in Liberal opinion to offset the bias in land line only telephone polls.