Reliability
The two types of reliability criteria that determine the quality of a research study are (a) the reliability of the study and (b) the reliability of the research instruments. Reliability is the extent to which other researchers could arrive at the same or similar results if they conducted the same study with the same participants or subjects using the exact same procedures as you.
In reference to reliability of the research instruments, reliability is the degree to which the instruments consistently measure what the instrument is designed to measure. Reliability is measured numerically. For example, a coefficient over .60 (Cronbach's alpha) would indicate an acceptable reliability. A standard error of measurement is another way to express reliability. Cronbach's alpha in the high .90s might indicate multicollinearity (the questions on an instrument are measuring EXACTLY the same thing and not different dimensions of the same variable).