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#include "test_statistics.h"
#include <sstream>
BinomialMatcher::BinomialMatcher( const int num_samples, const double p,
const double max_deviation ) :
num_samples_( num_samples ),
p_( p ),
max_deviation_( max_deviation )
{
// Binomial expectation is np, variance is np(1-p).
// So we want | obs - np | <= max_deviation * sqrt( np(1-p) )
expected_ = num_samples_ * p_;
margin_ = max_deviation_ * std::sqrt( num_samples_ * p_ * ( 1 - p_ ) );
}
bool BinomialMatcher::match( const int &obs ) const
{
return expected_ - margin_ <= obs && obs <= expected_ + margin_;
}
std::string BinomialMatcher::describe() const
{
std::ostringstream os;
os << "is from Bin(" << num_samples_ << ", " << p_ << ") [" <<
( expected_ - margin_ ) << " <= obs <= " << ( expected_ + margin_ ) << "]";
return os.str();
}
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