Item-total correlation

The item-total correlation test is performed to check whether any item is not consistent with the rest of the scale and thus can be discarded. The analysis is performed to purify the measure by eliminating ‘garbage’ items prior to determining the factors that represent the construct. This can be done by measuring the correlation between the scores of an individual item and the sum of the scores of the remaining items that form the scale. In a reliable scale, all items should correlate with the total. A small item-correlation provides empirical evidence that the item is not measuring the same construct measured by the other scale items. A correlation value less than 0.3 indicates that the corresponding item does not correlate very well with the scale overall and, thus, it may be dropped .