RAND-IAQL-4 Scoring Procedure and Translation Table

Scoring Procedure

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

References

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.

Scoring Table

Sum Score T-Score SE
0 36.2 5.7
1 41.8 4.0
2 45.1 3.4
3 47.5 3.1
4 49.4 3.0
5 51.1 2.9
6 52.7 2.8
7 54.2 2.8
8 55.6 2.8
9 57.0 2.7
10 58.4 2.7
11 59.8 2.7
12 61.3 2.8
13 62.9 2.9
14 64.7 3.1
15 66.9 3.3
16 71.3 4.6
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.