"It is very important to understand the following point. Probability theory always gives us the estimates that are justified by the information that was actuall

"It is very important to understand the following point. Probability theory always gives us the estimates that are justified by the information that was actually used in the calculation. Generally, a person who has more relevant information will be able to do a different (more complicated) calculation, leading to better estimates. But of course, this presupposes that the extra information is actually true. If one puts false information into a probability calculation, then the probability theory will give optimal estimates based on false information: these could be very misleading. The onus is always on the user to tell the truth and nothing but the truth; probability theory has no safety device to detect falsehoods." G. L Bretthorst, "Baysian Spectrum Analysis and Parameter Estimation," Springer-Verlag series 'Lecture Notes in Statistics' # 48, 1988, p30-31.