Statistics Assignment

statsassignment.java

import java.lang.reflect.Array;
import java.util.Arrays;

/**
 * kevinstewart at 15-05-26.
 */
public class Main {

    public static void main(String[] args) {
        // Define data sets
        double[] dataSetA = {1.95, 1.51, 2.15, 3.53, 5.22, 1.04, 1.03, 1.47 };
        double[] dataSetB = {4.4, 5.2, 4.8, 5.7, 4.3, 4.1, 4.2, 4.1, 5.6, 5.1, 4.9};

        double datasetAMean = calculateMean(dataSetA);
        double datasetBMean = calculateMean(dataSetB);

        double datasetAMedian = calculateMedian(dataSetA);
        double datasetBMedian = calculateMedian(dataSetB);

        double datasetAStdDev = calculateStDev(dataSetA, datasetAMean);
        double datasetBStdDev = calculateStDev(dataSetB, datasetBMean);

        double datasetASkew = calculateSkew(datasetAMean, datasetAMedian, datasetAStdDev);
        double datasetBSkew = calculateSkew(datasetBMean, datasetBMedian, datasetBStdDev);

        System.out.println("---- Dataset A ----");
        System.out.println("Mean: " + datasetAMean);
        System.out.println("Median: " + datasetAMedian);
        System.out.println("Standard Deviation: " + datasetAStdDev);
        System.out.println("Skew: " + datasetASkew);

        System.out.println("---- Dataset B ----");
        System.out.println("Mean: " + datasetBMean);
        System.out.println("Median: " + datasetBMedian);
        System.out.println("Standard Deviation: " + datasetBStdDev);
        System.out.println("Skew: " + datasetBSkew);



    }

    /**
     * Calculates and returns average
     * @param dataset array of doubles
     * @return array's mean (average)
     */
    private static double calculateMean(double[] dataset) {
        double sum = 0;
        for (int i=0; i < dataset.length; i++) {
            sum += dataset[i];
        }

        return sum / dataset.length;
    }

    /**
     * Returns median of an unsorted (or sorted) data set
     * @param dataset array of doubles
     * @return median of data set
     */
    private static double calculateMedian(double[] dataset) {
        Arrays.sort(dataset);
        if (dataset.length % 2 == 0) {
            return (dataset[dataset.length / 2] + dataset[(dataset.length / 2) - 1]) / 2.0;
        } else {
            return dataset[dataset.length/2];
        }
    }

    /**
     * Returns standard deviation of an array of doubles
     * @param dataset array of doubles
     * @param mean mean of dataset
     * @return standard deviation
     */
    private static double calculateStDev(double[] dataset, double mean) {
        double[] workingset = new double[dataset.length];
        double sum = 0;
        for (int i = 0; i < workingset.length; i++) {
            workingset[i] = Math.pow(dataset[i] - mean, 2.0);
            sum += workingset[i];
        }
        return (Math.sqrt(sum / (double)workingset.length));

    }


    /**
     * Returns skew of dataset
     * @param dataset array of doubles
     * @param mean mean of dataset
     * @param median median of dataset
     * @param stdDev standard deviation of dataset
     * @return
     */
    private static double calculateSkew(double mean, double median, double stdDev) {
        return ((mean - median) * 3.0) / stdDev;
    }
}