Omnibus Survey is a type of marketing research, commonly organized by marketing research companies in which different cross sections of the community are interviewed by the method of stratified sampling. As sampling and screening costs are shared across multiple clients, so this method is cost effective. The sample size of an omnibus survey is usually large and interviews go on.
Each omnibus survey has a designated number of questions available to each participating client. To be fair to all clients, it avoids unusually long question sets with open-ended questions or wordy questions / response options. Each client is also restricted to a certain length in minutes.