Accord.Statistics.Testing.Power.ZTestPowerAnalysis.ComputeEffect C# (CSharp) Method

        public override void ComputeEffect()
        {
            double Za = ZTest.PValueToStatistic(Size, Tail);
            double Zb = NormalDistribution.Standard
                    .InverseDistributionFunction(Power);

            double n = Math.Sqrt(Samples);
            double d = (Za + Zb) / n;

            Effect = d;
        }

        /// <summary>
        ///   Estimates the number of samples necessary to attain the
        ///   required power level for the given effect size.
        /// </summary>
        ///
        /// <param name="sampleSize">The number of observations in the sample.</param>
        /// <param name="power">The desired power level. Default is 0.8.</param>
        /// <param name="alpha">The desired significance level. Default is 0.05.</param>
        /// <param name="hypothesis">The alternative hypothesis (research hypothesis) to be tested.</param>
        ///
        /// <returns>The required number of samples.</returns>
        ///
        public static ZTestPowerAnalysis GetEffectSize(int sampleSize, double power   = 0.8, double alpha = 0.05,
                                                       OneSampleHypothesis hypothesis = OneSampleHypothesis.ValueIsDifferentFromHypothesis)
        {
            var analysis = new ZTestPowerAnalysis(hypothesis)
            {
                Samples = sampleSize,
                Size    = alpha,
                Power   = power,
            };

            analysis.ComputeEffect();

            return(analysis);
        }