Reliability

In statistics, reliability is the consistency of a measurement.A measurement has a high reliability if it consistently produces the same or similar results under the same conditions.A sample cannot be entirely representative of the population in the habitat.The sample may not be representative for one of two reasons.Firstly, there may be unintentional bias if humans are doing the choosing.Alternatively, the sample may be unrepresentative due to chance.A small sample size increases the risk of the sample being unrepresentative.Reliability does not imply validity. If a measurement is consistent it is reliable, but it is not necessarily measuring what is supposed to be measured.However, a test that is not perfectly reliable cannot be perfectly valid.