The accuracy and biases of diary communication data

A study to determine the accuracy and reliability of telephone communications data obtained via self-recording diaries was undertaken. The methodology involved comparing data obtained from the diaries to the more objective data provided by the recording capabilities of a PBX (Private branch Exchange). Two questions formed the basis for the analysis. First, what is the level of accuracy of diary data, and, second what biases are inherent in data obtained from self-recorded diaries. The findings indicate that diary data significantly understate the actual frequency of communications. There were also several biases inherent in the diary data. One involved a significant understatement of very short communications (i.e. those lasting less than 90 seconds). The others showed an under-recording of received calls and a likelihood to record internal rather than external cals. The conclusion drawn is that in the absence of objective data (i.e. data obtained from machine recording) diaries can provide usable data as long as one pays attention to the biases inherent in their use.