I. Topic: Reliability and Validity in Measuring Intelligence

II. Purpose: To help students understand better the nature of reliability and validity in measuring psychological phenomena, in this case, intelligence.

III. Description: Handout

Reliability and Validity are often difficult concepts for student to apply in their thinking about tests and measurements. This handout asks students to identify particular problems to which one old, but very interesting, measure of intelligence is susceptible.

IV. Procedure:

1. Ask students to read the following handout and reply to the questions it contains. Have students share their answers to these items in class. Discuss with them the meaning of the terms reliability and validity and how they apply to Morgan's procedure in his research on intelligence.

S. G. Morgan, a well-known 19th century scientist argued that intelligence among different races differs as a function of head size--the larger the head, the more intelligent the person. Extending this logic, if people of a particular race tend to have larger heads that people of another race, then its members may be said to be more intelligent than members of that other race. To test his ideas, he gathered craniums from different human races and filled them with sifted mustard seed. He then poured the sifted seed back into a graduated cylinder to determine the skull's volume in cubic inches.

State Morgan's hypothesis.

Was Morgan's method a reliable measure of intelligence--why or why not?

Was Morgan's method a valid measure of intelligence--why or why not?