/// <summary>
/// Construct a Chi-Square Test.
/// </summary>
/// <param name="expected">The expected variable values.</param>
/// <param name="observed">The observed variable values.</param>
/// <param name="degreesOfFreedom">The chi-square distribution degrees of freedom.</param>
/// <param name="threshold">The significance threshold. By default, 0.05 will be used.</param>
///
public ChiSquareTest(double[] expected, double[] observed, int degreesOfFreedom, double threshold)
{
if (expected == null)
{
throw new ArgumentNullException("expected");
}
if (observed == null)
{
throw new ArgumentNullException("observed");
}
// X² = sum(o - e)²
// -----
// e
double sum = 0.0;
for (int i = 0; i < observed.Length; i++)
{
double d = observed[i] - expected[i];
sum += (d * d) / expected[i];
}
this.Statistic = sum;
this.Threshold = threshold;
this.distribution = new ChiSquareDistribution(degreesOfFreedom);
this.PValue = distribution.SurvivalFunction(Statistic);
}
/// <summary>
/// Constructs a Chi-Square Test.
/// </summary>
/// <param name="statistic">The test statistic.</param>
/// <param name="degreesOfFreedom">The chi-square distribution degrees of freedom.</param>
/// <param name="threshold">The significance threshold. By default, 0.05 will be used.</param>
///
public ChiSquareTest(double statistic, int degreesOfFreedom, double threshold)
{
this.Statistic = statistic;
this.Threshold = threshold;
this.distribution = new ChiSquareDistribution(degreesOfFreedom);
this.PValue = distribution.SurvivalFunction(Statistic);
}
//---------------------------------------------
private void compute(double[] observed, double[] expected)
{
// X² = sum(o - e)²
// -----
// e
double sum = 0.0, d;
for (int i = 0; i < observed.Length; i++)
{
d = observed[i] - expected[i];
sum += (d * d) / expected[i];
}
this.Statistic = sum;
this.PValue = distribution.SurvivalFunction(Statistic);
}
