... world of marketing havebeen able to rely on a small number of reasonably methodologicallysound sources of marketing data. But today, increasingly, we are facedwith more information, much of which ... researcher can offsetmuch potential source of bias through careful questionnaire design (andskilful interviewing). Even the most professional of surveys will notwholly counteract biases of this kind, ... of visitors to theexhibition will have failed to capture the opinions of a groupinstrumental to any assessment of the success of the event.·Too shallow. In some situations a description of...