MISSING DATA IN LIKERT RATINGS - A COMPARISON OF REPLACEMENT METHODS

The effects of using two methods (item mean and person mean) for repla cing missing data in Likert scales were studied. The results showed th at both methods were good representations of the original data when bo th the number of respondents with missing data and the number of items missing were 20% or less. As the numbers of missing items and of resp ondents with missing data increased for the person mean substitution m ethod, a spurious increase in the inter-item correlations (and, theref ore, reliability) for the scale was produced. The item mean substituti on reduced the reliability estimates of the scale. These results sugge st caution in the use of the person mean substitution method as the nu mbers of missing items and respondents increase.