The reliability and validity of the test was shown to be very strong with reliability coefficients ranging from .77 to .89 in different studies and a strong correlation with scores of other common instrument. The tool was also shown to be valuable across several settings from clinical, through counseling to research purposes and finally, the strength and weakness of the instrument were considered.
The Beck Depression Inventory is a psychological test that is widely acknowledge and accepted. The test was first created by Beck and his colleagues in the 1960s; however, since then the reliability and validity of the instrument have been examined in several languages amongst several populations and the general efficiency of the test as an instrument for measuring cognitive values has been widely established. The Beck Depression Inventory comes in questionnaire form that allows for self evaluation based on a point grade system of the questions contained in the questionnaire.
Arnault, Saint, Shinji Sakamoto, Aiko Moriwaki (2006) reports that a study has been carried out with a Japanese population that validated the use of the instrument, Chellappa and Arajo 2006 also reported a validation of a Portuguese version of the test among a Brazilian sample, while Carano et al. (2006) also reported a stock taking and evaluation of the Psychometric properties of the test after twenty five years carried out by Beck et al (1988)
Obviously, Beck Depression Inventory has undergone serious and several tests of validity, reliability and efficiency, and in most cases, the value of the instrument in measuring depressive symptoms have been credibly established.
Purpose, Design and Format of Beck Depression Inventory
In the commonest cases, and perhaps, as the name of the instrument suggests; Beck Depression Inventory is an instrument that is used for taking 'inventory' of the depressive tendencies and/or depressive symptoms in a sample population. It is sometimes used in conjunction with other psychological tests to evaluate other forms of cognitive values, for instance, Zywiak et al (2006) made use of BDI as an instrument to predict negative affect relapses in men undergoing formal treatment for alcoholism. However, in most cases, Beck Depression Inventory is aimed at measuring the severity of depression in a population. The questions of the instrument are so designed as to evaluate the patients' self report of activities, moods and behaviors for signs of depression symptoms and the severity of the symptoms, if present.
In this regard, the instrument contains twenty one items that focuses majorly on the cognitive symptoms of depression. Each items in the instrument is rated on a four-point Likert-type scale with scores ranging from 0 - 3. The sum of the points of all the items in the instrument indicates the BDI score of the client, which is also an indication of the presence or otherwise, and the severity of depression in the client. The total possible score of the instrument is 84. A BDI score of between 0 and 9 is regarded as lack of, or minimal depression, total BDI scores of 10 - 18 is an indication of mild depression, while a total BDI score of 19 - 29 is an indication of moderate depression, any score above 29 is an indicati