Psychometric Properties of the Spanish Full and Short Forms of the System Usability Scale (SUS): Detecting the Effect of Negatively Worded Items
Diana Castilla, Irene Jaén, Carlos Suso‐Ribera, Gemma García‐Soriano, Irene Zaragozá, Juana Bretón‐López, Adriana Mira, Amanda Díaz‐García, Azucena García‐Palacios
Abstract
This study examined the SUS’s psychometric properties with the Spanish population considering the plausible method effects associated with negatively worded items. A short form consisting of either direct or reversed items was also examined. Participants were 1321 Spaniards who completed the SUS. Confirmatory analyses showed that the SUS was a valid measure with a one-factor structure when method errors associated with negatively worded items were considered (CFI = .932, TLI = .898; RMSEA = .055, CI 90% = 0.047, 0.062), and shown evidence of reliability (Cronbach’s alpha = .76). The short version with only positively worded items also showed to be a valid (CFI = .973, TLI = .946; RMSEA = .057, CI 90% = .041, .075) and reliable measure (Cronbach alpha = .77) to assess usability. This is the first study to clarify the effect of negatively worded items in the structure of the SUS and propose a short version of the SUS to be used with Spaniards when a brief version is preferred to test usability.