What Is Item Analysis?

Item analysis is done to see if the items in the instrument belong there or not. Each item is examined for its ability to discriminate between those subjects whose total scores are high and those with low scores. In item analysis the means between the high-score group and the low-score group are tested to detect significant differences through the t-values. The items with a high t-value are then included in the instrument. Thereafter tests for the reliability of the instrument are done and the validity of the measure is established.

Very briefly reliability tests how consistently a measuring instrument measures whatever concepts it is measuring. Validity tests how well an instrument that is developed measures the particular concept it is intended to measure. In other words validly is concerned with whether we measure the right concept and reliability with the stability and consistency of measurement. Validity and reliability of the measure attest to the scientific rigor that has gone into the research study.

These two criteria will now be discussed. The reliability of a measure indicates the extent to which it is without bias and hence ensures consistent measurement across time and across the various items in the instrument. The reliability of a measure is an indication of the stability and consistency with which the instrument measure the concept and helps to assess the goodness of a measure.