Created
May 26, 2009 18:05
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class Fairish | |
def initialize(probability, unfair_low, unfair_high, min_rolls) | |
@probability, @unfair_low, @unfair_high, @min_rolls = probability, unfair_low, unfair_high, min_rolls | |
@rolls, @hits = 0, 0 | |
end | |
def fire! | |
hit = if @rolls >= @min_rolls && observed_probability > @unfair_high | |
false | |
elsif @rolls >= @min_rolls && observed_probability < @unfair_low | |
true | |
else | |
rand <= @probability | |
end | |
@hits += 1 if hit | |
@rolls += 1 | |
return hit | |
end | |
private | |
def observed_probability | |
@hits.to_f / @rolls | |
end | |
end | |
class Random | |
def initialize(probability) | |
@probability = probability | |
end | |
def fire! | |
rand <= @probability | |
end | |
end | |
trials = 100000 | |
trial_size = 10 | |
random_out_of_bounds_low = 0 | |
random_out_of_bounds_high = 0 | |
fairish_out_of_bounds_low = 0 | |
fairish_out_of_bounds_high = 0 | |
probability = 0.2 | |
lower_bound = 0.1 | |
upper_bound = 0.4 | |
min_rolls = trial_size / 2 | |
trials.times do |n| | |
fairish = Fairish.new probability, lower_bound, upper_bound, min_rolls | |
fairish_hits = 0 | |
random = Random.new probability | |
random_hits = 0 | |
trial_size.times do |x| | |
fairish_hits += 1 if fairish.fire! | |
random_hits += 1 if random.fire! | |
end | |
fairish_out_of_bounds_low += 1 if fairish_hits.to_f / trial_size < lower_bound | |
fairish_out_of_bounds_high += 1 if fairish_hits.to_f / trial_size > upper_bound | |
random_out_of_bounds_low += 1 if random_hits.to_f / trial_size < lower_bound | |
random_out_of_bounds_high += 1 if random_hits.to_f / trial_size > upper_bound | |
end | |
puts "Fairish was out of bounds #{(fairish_out_of_bounds_low + fairish_out_of_bounds_high).to_f/trials * 100}% of the time (#{fairish_out_of_bounds_low.to_f/trials * 100}% low and #{fairish_out_of_bounds_high.to_f/trials * 100}% high)." | |
puts "Random was out of bounds #{(random_out_of_bounds_low + random_out_of_bounds_high).to_f/trials * 100}% of the time (#{random_out_of_bounds_low.to_f/trials * 100}% low and #{random_out_of_bounds_high.to_f/trials * 100}% high)." |
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