The key difference between validity and reliability is that validity of test refers to the degree to which a test measures what it is supposed to measure, and reliability refers to the degree that a test is consistent. For example, IQ test has a high validity as an intelligence test. A test that requires applicants to write down the 12 numbers they view in 30 seconds will be a validity test for short term memory, but it will have a low validity as a test for long term memory.

Criterion validity: is proven by showing the evidence that people who score high in the test may perform well in the future job. The test content is not limited only to ability or skills. It could be personality, attitude, IQ, EQ, or any qualification required for the job. If applicants who have college degree will perform better than those who don't have the college degree in their future job, then we can say requirement of a college degree has criterion validity. In this case, whether one has a college degree or not is a test for employee selection.In another example, if people with high IQ turn out to be good performers in the future job, then IQ test has high criterion validity.

Content validity: if a selection test includes samples of tasks that are performed in the job, then the test has high content validity. For example, if a test used for selecting secretaries includes test content like typing, filing, answering the phone, etc, then the test has a high content validity.

A test has a high level of reliability if 1) same test takers score similar in the same test at two different times (test retest reliability), 2) same test takers score similar in two tests supposed to measure the same concept, principle or subject (equivalent form reliability), and 3)same test takers respond similarly to similar questions supposed to measure the same concept, principle or subject (internal consistency).

Question 2

In the case of Griggs vs. Duke Power, Duke Power required a high school diploma for the position of coal handler. This job requirement screened out many African American applicants, which led to the lawsuit of discrimination by Griggs against the company Duke Power. What do you think the job requirement lacked, validity or reliability? Why?