فائل:Pvalue hypothesis testing.png

// Scilab script for P-value
function [y]=normpdf(x)
y=1/sqrt(2*%pi)*exp(-x.^2/2);
endfunction
//
MAX=3.5;
x=[-MAX:.1:MAX]; // X-axis values
y=normpdf(x); // normal pdf (Y-axis)
Pth=2.197286; // threshold
//
// polygon for the right red region
x1=[Pth:.1:MAX];
y1=normpdf(x1);
x2=[x1 x1(1)];
y2=[y1 y1(length(y1))];
//
// polygon for the left red region
x3=[-MAX:.1:-Pth];
y3=normpdf(x3);
x4=[x3 x3(length(x3))];
y4=[y3 y3(1)];
//
// marker for the threshold
format("v",10);
plot([Pth Pth],[0 .1],'--m');
xstring(Pth,.11,["y =" string(Pth)]);
//
format("v",6);
xset('color',5);
xfpoly(x2,y2); // draw the right filled polygon
xfpoly(x4,y4); // draw the left filled polygon
xset('color',1);
plot(x,y); // draw the normal pdf curve
//
// area under the curve in the right red filled polygon
Area=erfc(Pth/sqrt(2))/2;
xstring(0,0,["area=" string(Area)]);
text=gce();//get the handle for the text string
text.data=[2.5,.02];
xstring(0,0,["area=" string(Area)]);
text=gce();//get the handle for the text string
text.data=[-3.8,.02];
text.foreground=5;
//
xstring(0,0,["P-value=" string(2*Area)]);
text=gce();
text.data=[2,.2];
title('standard normal probability density function');
a=get("current_axes");//get the handle of the newly created axes
a.data_bounds=[-4,0;4,.45];