text: In<unk> s, an<unk>  is a<unk>  whose probability distribution does not depend on which of the probability distributions among those being considered is the distribution of the<unk> al population from which the data were taken.  This concept was introduced by the great<unk> al geneticist Sir Ronald Fisher.
option_0: Ancillary statistic
option_1: Absolute deviation
option_2: Hazard ratio
option_3: Degrees of freedom 
option_4: Quantum yield
option_5: Allan variance
option_6: Non-parametric statistics
option_7: Attributable risk