概率论实验报告
信息45 刘兆行2140502113 问题2:
源程序:
fun=inline('(1/(sqrt(2*pi)*0.5))*exp(-(x-1.5).^2/(2*0.5^2))','x'); I1=quad(fun,1.8,2.9)
I2=quad(fun,-2.5,10)
t=2.4;
I3=quad(fun,-10,t);
while(I3>0.95)
t=t-0.0001;
I3=quad(fun,-10,t);
end
t
x=-4:0.01:8;
y1=(1/(sqrt(2*pi)*0.5))*exp(-(x-1).^2/(2*0.5^2));
y2=(1/(sqrt(2*pi)*0.5))*exp(-(x-2).^2/(2*0.5^2));
y3=(1/(sqrt(2*pi)*0.5))*exp(-(x-3).^2/(2*0.5^2));
plot(x,y1,'r-')
hold on
plot(x,y2,'b--')
hold on
plot(x,y3,'g-')
程序运行结果:
问题3:
卡方分布:
源程序:
w=0:0.01:50;
k1=chi2pdf(w,3); k2=chi2pdf(w,10); k3=chi2pdf(w,20); plot(w,k1,'r-') hold on
plot(w,k2,'b--') hold on
plot(w,k3,'g-')
运行结果:
t分布:
源程序:
x=-5:0.01:5;
t1=tpdf(x,5); t2=tpdf(x,10); t3=tpdf(x,100); plot(x,t1,'r-') hold on
plot(x,t2,'b--') hold on
plot(x,t3,'g-') 运行结果:
F分布:
源程序:
u=0:0.01:8;
f1=fpdf(u,10,100); f2=fpdf(u,10,10); f3=fpdf(u,10,5); plot(u,f1,'r-') hold on
plot(u,f2,'b--') hold on
plot(u,f3,'g-')
运行结果:
t分布与标准正态分布的比较:
源程序:
X=-8:0.01:8;
Y1=tpdf(X,4);
Y2=normpdf(X,0,1);
plot(X,Y1,'r-',X,Y2,'b--')
XX=-8:0.01:8;
YY1=tpdf(XX,40);
YY2=normpdf(XX,0,1);
plot(XX,YY1,'r-',XX,YY2,'b--')
运行结果:
问题4:
源程序:
n=10000;
x=rand(n,1);
for y=1:5
w1=0;
for i=1:n
if x(i)<0.05
d=0;
elseif x(i)<0.15
d=1;
elseif x(i)<0.40
d=2;
elseif x(i)<0.75
d=3;
elseif x(i)<0.90
d=4;
else
d=5;
end
if y>d
w=14*d-8*(y-d);
else
w=14*y;
end
w1=w1+w;
end
y
w1
end
运行结果:
问题5
源程序:
d=1;
r=0.6;
m=0;
n=10000;
x=unifrnd(0,d/2,1,n); phi=unifrnd(0,pi,1,n); for i=1:n
if x(i) m=m+1; end end frequency=m/n pi=2*r/(d*frequency); 运行结果: