Bias: adding to the uncertainty.
Sparrow
J M
JM
Thompson
J R
JR
D015982:Bias; D015986:Confounding Factors, Epidemiologic; D005124:Eye Abnormalities / Q000453:epidemiology; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D015983:Selection Bias