A parametric analysis of ordinal quality-of-life data can lead to erroneous results.

@article{citeulike:2665278, abstract = {OBJECTIVE: Measurements from health-related quality-of-life (HRQoL) studies, although usually of an ordered categorical nature, are typically treated as continuous variables, allowing the calculation of mean values and the administration of parametric statistics, such as t-tests. We investigated whether parametric, compared to nonparametric, analyses of ordered categorical data may lead to different conclusions. STUDY DESIGN AND SETTING: HRQoL data were obtained from patients with a diagnosis of asthma (n=192) and chronic obstructive pulmonary disease (COPD; n=88) at two time points. The impact of the group factor (asthma vs. COPD) and the time factor (t1 vs. t2) on HRQoL was analyzed with a metric approach (repeated measures ANOVA) and two ordinal approaches (each with a nonparametric repeated measures ANOVA). RESULTS: Using the metric approach, a significant effect of "group" (P=0.0061) and "time" (P=0.0049) on HRQoL was found. The first ordinal approach (ranked total score) still showed a significant effect for "group" (P=0.0033) with a worse HRQoL for patients suffering from COPD. In the second approach (ranks for each HRQoL item and summed ranks), there were no significant effects. CONCLUSION: Applying simple parametric methods to ordered categorical HRQoL scores led to different results from those obtained with nonparametric methods. In these cases, an ordinal approach will prevent inappropriate conclusions.}, address = {Department of Medical Statistics, University of G\"{o}ttingen, Humboldtallee 32, D-37073 G\"{o}ttingen, Germany.}, author = {Kahler, E. and Rogausch, A. and Brunner, E. and Himmel, W. }, citeulike-article-id = {2665278}, doi = {10.1016/j.jclinepi.2007.05.019}, issn = {0895-4356}, journal = {Journal of clinical epidemiology}, month = {May}, number = {5}, pages = {475--480}, posted-at = {2008-04-14 05:20:39}, priority = {2}, title = {A parametric analysis of ordinal quality-of-life data can lead to erroneous results.}, url = {http://dx.doi.org/10.1016/j.jclinepi.2007.05.019}, volume = {61}, year = {2008} }

TY - JOUR ID - citeulike:2665278 L3 - citeulike-article-id:2665278 TI - A parametric analysis of ordinal quality-of-life data can lead to erroneous results. JF - Journal of clinical epidemiology VL - 61 IS - 5 SP - 475 EP - 480 AD - Department of Medical Statistics, University of Göttingen, Humboldtallee 32, D-37073 Göttingen, Germany. SN - 0895-4356 N2 - OBJECTIVE: Measurements from health-related quality-of-life (HRQoL) studies, although usually of an ordered categorical nature, are typically treated as continuous variables, allowing the calculation of mean values and the administration of parametric statistics, such as t-tests. We investigated whether parametric, compared to nonparametric, analyses of ordered categorical data may lead to different conclusions. STUDY DESIGN AND SETTING: HRQoL data were obtained from patients with a diagnosis of asthma (n=192) and chronic obstructive pulmonary disease (COPD; n=88) at two time points. The impact of the group factor (asthma vs. COPD) and the time factor (t1 vs. t2) on HRQoL was analyzed with a metric approach (repeated measures ANOVA) and two ordinal approaches (each with a nonparametric repeated measures ANOVA). RESULTS: Using the metric approach, a significant effect of "group" (P=0.0061) and "time" (P=0.0049) on HRQoL was found. The first ordinal approach (ranked total score) still showed a significant effect for "group" (P=0.0033) with a worse HRQoL for patients suffering from COPD. In the second approach (ranks for each HRQoL item and summed ranks), there were no significant effects. CONCLUSION: Applying simple parametric methods to ordered categorical HRQoL scores led to different results from those obtained with nonparametric methods. In these cases, an ordinal approach will prevent inappropriate conclusions. AU - Kahler, E AU - Rogausch, A AU - Brunner, E AU - Himmel, W PY - 2008/05// UR - http://dx.doi.org/10.1016/j.jclinepi.2007.05.019 ER -