Seventh, because the immune system is weak it cannot kill enough cancer cells and the cancer cells grow out of control. Thus, in summary, the root cause of cancer is microbes and parasites that are in the organs or colon (or bloodstream), which weakens the immune system. However, other things can cause cancer.
Test Reliability and Validity Defined Reliability. Test reliablility refers to the degree to which a test is consistent and stable in measuring what it is intended to measure. Most simply put, a test is reliable if it is consistent within itself and across time.
Reliability and Validity. Reliability and validity, as the terms are used in scientific study, are characteristics of the dependent variable and the specific operational definition. In analyzing a study, after the dependent variables and their operational definitions are identified, their reliability and validity must be established.