When you can logically conclude that your independent variable is causal with respect to the dependent variable, you are implying that your measurements are showing

American and British English are considered to be mutually __________ because the speakers of either dialect can usually understand speakers of the other dialect.

Fill in the blank(s) with the appropriate word(s).

Emmanuel recently completed the Critical Reasoning Test (CRT) for the third time in three years. The first time Emmanuel attained a score that was near the top of the scale. The second time he took this test he scored near the bottom. The last time his score was right near the middle of the scores for the test. Emmanuel's differing performance each time he takes this test suggests that the test:

a. has poor validity b. has not been adequately standardized c. is measuring something other than critical reasoning skills d. has low test-retest reliability