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Biomedical subjects

L J Chapman

Publications and source records attributed to L J Chapman.

At least 73 records · Page 4Linked to original sources
PubMed1975

Schizophrenic reasoning about affect-laden material.

Drug-free schizophrenic patients (N equals 74) and nonpsychotic subjects (N equals 206) were given a test of affect-laden and affectively neutral multiple choice analogy items. The two subtests were matched on several psychometric characteristics that determine the power of the test to distinguish the more able from the less able normal subjects. Neither newly admitted schizophrenic nor long-term chronic schizophrenic patients performed differently on the affective subtest than on the neutral subtest. The many published findings of a cognitive deficit in schizophrenia in response to affect-laden stimuli can probably be attributed to the inappropriate use of unmatched tested.

Adult↗
PubMed1975

Alternatives to the design of manipulating a variable to compare retarded and nonretarded subjects.

In the design of manipulating a single variable to compare the performance of retarded and nonretarded subjects, the groups' response to the variable cannot demonstrate a loss of ability of retarded subjects. This is because tasks (measures at points on the variable) which differ on difficulty or on reliability also differ in power to distinguish subjects of differing ability. A solution is to hypothesize a differential deficit (greater deficit in response to one variable than another) and manipulate two variables. The tasks should be matched at all difficulty levels on reliability, mean, and variance of item difficulty and shape of the distribution of item difficulty.

Educational Measurement↗