The reduced discounting inventory - construction and initial validation

Abstract

In two studies, the aim of this research was to develop and validate a Polish version of the reduced Discounting Inventory. In Study 1 (N = 623) items extraction from the 48-item DI was based upon item-total correlation and items with highest coefficients were considered. The reduced Discounting Inventory resulted in sixteen items. Cronbach’s a coefficient was .78, and the item-total correlations ranged between .59 and .77. The correlation between Polish versions of reduced Discounting Inventory and longer 48-item Discounting Inventory was .85. Next, the reduced Discounting Inventory was evaluated in terms of factorial and construct validity. The structure of the instrument was analysed by Confirmatory Factor Analyses procedure. It indicated that the four-factor structure had the best fit to the data. Additionally, we show that this reduced Discounting Inventory closely parallels the longer 48-item inventory its relation to traditional discounting measures using pairs of hypothetical choices (expect for the delay discounting subscale). Finally, in study 2, the test-retest reliability of the reduced Discounting Inventory over a 3-month interval was assessed (247 subjects of the 623 individuals who participated in Study 1). Results indicated good stability of the reduced measure (≥ .88). It is concluded that the reduced Discounting Inventory has notable psychometric properties and that it can serve as an alternative measure of discounting when situations do not allow the use of longer inventories.