View source for User Reference:StimulusPresentationTask

====Random Sequence:====

The investigator defines absolute stimulus frequencies for each stimulus, with the sum <math>N</math> of those values equaling the total number of stimulus presentations in the final sequence. The resulting random sequence is obtained by applying a random permutation to an arbitrary sequence that reproduces the given frequencies, with all <math>N!</math> index permutations being equally probable (Block Randomization).

As an example: 
  
6 2 3
 
defines a sequence of 11 stimulus presentations with stimulus 1 being presented 6 times, stimulus 2, 2 times, and stimulus 3, 3 times. The resulting sequence <math>S_1</math> will be a permutation of <math>S_0 = [1, 1, 1, 1, 1, 1, 2, 2, 3, 3, 3]</math>, and the probability for <math>S_1</math> to equal <math>S_0</math> will be <math>\frac{6!\times2!\times3!}{(6+2+3)!}=1/4620</math>.

Multiple sequences can be generated from the given frequencies. The investigator can define how many sequences are generated and presented.