RAND-IAQL-4 Scoring Procedure and Translation Table
Each of the four items on the RAND-IAQL-4 use five-category response options ranging in value from 0 to 4. Higher scores indicate greater negative impact of asthma on quality of life. In cases where the items have been administered on a range 1 to 5, first re-score response options for each item to 0 to 4 (e.g., 1=0, 2=1, 3=2, 4=3, 5=4). To find the total raw score, sum across the values of the responses to all four questions. The lowest possible score will be 0 and the highest possible score will be 16. If any of the four items are missing, assign the respondent a missing value for the total score.
Next, based on a given total score, find the associated IRT-score in the “T-Score” column. The “T-Score” column provides the IRT-based asthma quality of life score score estimate given each particular total score. Note that the “T-Score” and “SE” columns transform the IRT metric (N(mean=0, standard deviation =1)) to a T-score metric (mean = 50, standard deviation = 10). A higher T-score means worse Asthma quality of life.RAND-IAQL Main Page
Thissen, D., Pommerich, M., Billeaud, K., & Williams, V.S.L. (1995). Item response theory for scores on tests including polytomous items with ordered responses. Applied Psychological Measurement, 19, 39-49.
Thissen, D., Nelson, L., Rosa, K., & McLeod, L.D. (2001). Item response theory for items scored in more than two categories. In D. Thissen & H. Wainer (Eds), Test Scoring (pp. 141-186). Mahwah, NJ: Lawrence Erlbaum Associates.
|Note: T-score metric is a linear transformation from the IRT theta scale: T-score = 10 * theta + 50.
SE in the table is the standard error on T-score metric.