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.
A measure is considered reliable if it would give us the same result over and over again (assuming that what we are measuring isn't changing!). Let's explore in more detail what it means to say that a measure is repeatable or consistent. We'll begin by defining a measure that we'll arbitrarily label X.