Disadvantages - Survey Research:

To fulfil the  evidence of  concomitant variation it is essential to select one  group of people  who have gone  through a particular experience and another group  of people who have not  gone  through the experience. It  is very difficult to assure such distinctions.

Mostly it is not  possible  to give a pre test before  the experience to assess the initial  comparability of the  two group  and to known  their position  in relation to the dependent variable.