  It is suggested to insert into test matrix 1s for correct responses, 0s for
response refusals, and negative corrective elements for incorrect responses.
With the classical test theory approach test scores of examinees and items are
calculated traditionally as sums of matrix elements, organized in rows and
columns. Correlation coefficients are estimated using correction coefficients.
In item response theory approach examinee and item logits are estimated using
maximum likelihood method and probabilities of all matrix elements.
