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Bias refers to a methodological flaw in a research study which prevents generalization of a sample population out to the entire population. It is a systematic error.
Errors in radiology research studies fall into one of two categories:
- random error
- systematic error/bias
Random error cannot be controlled, but it can be accounted for with the correct statistical technique. An appropriately low p-value improves our confidence that the results are not due to random error (usually set at <0.05 (5%) probability).
Systematic error/bias, on the other hand, cannot be accounted for with statistics. Non-random clustering of variable attributes can flaw our ability to generalize out to the general population. So can non-random gathering of the data by the radiology researcher.
There are multiple opportunities for bias to creep into a radiology study, some obvious and some subtle. It is the researcher's goal to eliminate any large biases and control or account for any smaller ones.