Welch's t-test: Difference between revisions
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+Java (could be better...)
m (Welch's t-test is only part of the calculation, it isn't the purpose of the page. Clarifying this in the task description) |
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0.0107377</lang>
=={{header|Java}}==
<lang java>import org.apache.commons.math3.distribution.TDistribution;
public class WelchTTest {
public static double[] meanvar(double[] a) {
double m = 0.0, v = 0.0;
int n = a.length;
for (double x: a) {
m += x;
}
m /= n;
for (double x: a) {
v += (x - m) * (x - m);
}
v /= (n - 1);
return new double[] {m, v};
}
public static double[] welch_ttest(double[] x, double[] y) {
double mx, my, vx, vy, t, df, p;
double[] res;
int nx = x.length, ny = y.length;
res = meanvar(x);
mx = res[0];
vx = res[1];
res = meanvar(y);
my = res[0];
vy = res[1];
t = (mx-my)/Math.sqrt(vx/nx+vy/ny);
df = Math.pow(vx/nx+vy/ny, 2)/(vx*vx/(nx*nx*(nx-1))+vy*vy/(ny*ny*(ny-1)));
TDistribution dist = new TDistribution(df);
p = 2.0*dist.cumulativeProbability(-Math.abs(t));
return new double[] {t, df, p};
}
public static void main(String[] args) {
double x[] = {3.0, 4.0, 1.0, 2.1};
double y[] = {490.2, 340.0, 433.9};
double res[] = welch_ttest(x, y);
System.out.println("t = " + res[0]);
System.out.println("df = " + res[1]);
System.out.println("p = " + res[2]);
}
}</lang>
'''Result'''
<pre>javac -cp .;L:\java\commons-math3-3.6.1.jar WelchTTest.java
java -cp .;L:\java\commons-math3-3.6.1.jar WelchTTest
t = -9.559497721932658
df = 2.0008523488562844
p = 0.010751561149784485<pre>
=={{header|Julia}}==
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