Psychometric evaluation of the Life Satisfaction Index-Z (LSI-Z) in an Iranian elderly sample

To assess the reliability and validity of the 13 item Life Satisfachtion Index-Z (LSI-Z) questionnaire in Kashan, Iran. The 13 item LSI- Z English version was translated into Persian through forward-backward method. Another questionnaire including demographic data and a question about overal life satisfaction status was also used. The sampling was performed using convenience method. All of the people aged ≥60 years old who had conferred to two health centers in kashan (a city in central part of Iran) (n=75) were selected. After their consent informed, the questionnaires were completed through interviews. Reliability was determined via internal consistency (cronbach’s alpha, split-half) and stability (test re-test). Construct validity was determined through known-groups comparison. The data were analyzed using Pearson correlation coefficient, Intraclass correlation coefficient, unequal spearman brown, Guttman, Cronbach’s alpha coefficient and one-way ANOVA. The life satisfaction score was 13.68±5.47 (from possible score ranging from 0 to 26). The questionnaire reliability coefficient (internal consistency) was 0.78-0.79. Item-total correlation and test-retest confirmed its reliability too. LSI-Z scores were significantly different among the 5 known- groups (P=0.0001, f=121.66); so the known-groups approach revealed that this tool is valid. The 13 item LSI-Z Persian version for evaluation of life satisfaction in Iranian elderly people is valid and reliable.