Reliability and Validity of Household Disaster Preparedness Index (HDPI)

The preparedness of families for disasters can set auspicious grounds for the preparedness of the whole society. In the health system of Iran, the Household Disaster Preparedness Index (HDPI) composed of 15 items is applied for the assessment ofhousehold preparedness in disasters.

The current study was carried out in order to investigate the reliability and validity of the HDPI.

Two methods, namely internal consistency and stability determination, were utilizedfor the investigation of HDPI reliability. Face validity, content validity, and construct validity were examined for the assessment of HDPI validity. Accordingly, in addition to interviewing with experts and family heads, 200 families were selected from a study population, including the families in all the counties of Isfahan province, Iran, based on multistage cluster sampling. Both qualitative and quantitative methods were used for the investigation of content validity. Furthermore, exploratory factor analysis was the method of choice for the examination of construct validity.

The rate of HDPI internal consistency was calculated at 0.786 which was within an acceptable range. Moreover, HDPI stability was computed at 0.98 using the test-retest method which was also within an optimal level. Therefore, it can be stated that the HDPI enjoys the required reliability. The investigation of HDPI face validity indicated that the families have problems in perceiving some of the items of this index. The experts put forward suggestions for the improvement of HDPI content validity following the qualitative investigation of content validity. In the examination of content validity ratio, all the items except those numbered 1, 3, and 4 were within an acceptable range; however, the investigation of the contentvalidity index demonstrated that only the validity of the items numbered 12 and 13 was acceptable regarding all the three scales of relevancy, clarity, and simplicity. For the determination of construct validity,exploratory factor analysis was applied toextract five factors (i.e., subscales), namely the reduction of vulnerability, planning for disasters, family empowerment, procurement of resources for disasters, and specialized programs. The investigation of the internal consistency of the aforementioned subscales indicated that only the internal consistency of the first and second factors was within an acceptable range.

The results of the present study revealed that although the HDPI is a reliable measure, it does not enjoy the required validity for the assessment of household preparedness for disasters