clg

graphsize 700,300

font "arial", 60,50

text 0,180,"<" :text 70,210,"<" : text 70,150,"<"

font "arial", 12,100

r1=0 : r2=0 : b1=0 : b2=0 : f=1.2

color yellow

rect 0,80,50,50 : rect 70,80,50,50

For y=1 to 4

For x=1 to 4

box1red=int(rand*f): box2red=int(rand*f)

box1blue=int(rand*(f-box1red)) : box2blue=int(rand*(f-box2red))

r1=r1+box1red : r2=r2+box2red

b1=b1+box1blue : b2=b2+box2blue

color red

if box1red=1 then circle x*10,80+y*10,3

if box2red=1 then circle 70+x*10,80+y*10,3

color blue

if box1blue=1 then circle x*10,80+y*10,3

if box2blue=1 then circle 70+x*10,80+y*10,3

next x

next y

color black

text 120,160,"P(RR)" :text 120,200,"P(RB)"

text 120,220,"P(BR)" : text 120,260,"P(BB)"

input "Redraw a ball at random from each box. What is the probability of each combination",a$

prr=(r1*r2)/((r1+b1)*(r2+b2)) : prb=(r1*b2)/((r1+b1)*(r2+b2))

pbr=(b1*r2)/((r1+b1)*(r2+b2)) : pbb=(b1*b2)/((r1+b1)*(r2+b2))

trr=0:trb=0:tbr=0:tbb=0

for n = 1 to 1000

draw=rand

if draw < prr then

trr=trr+1

print "RR"

end if

if prr < draw and draw < prr+prb then

trb=trb+1

Print "RB"

end if

if prr+prb < draw and draw < prr+prb+pbr then

tbr=tbr+1

Print "BR"

end if

if prr+prb+pbr < draw and draw < prr+prb+pbr+pbb then

tbb=tbb+1

Print "BB"

end if

rect 170,170,trr,5

rect 170,210,trb,5

rect 170,230,tbr,5

rect 170,270,tbb,5

next n

Print "Theorical probability"

print "P(RR)="+prr+"="+(r1*r2)+"/"+((r1+b1)*(r2+b2))

print "P(RB)="+prb+"="+(r1*b2)+"/"+((r1+b1)*(r2+b2))

print "P(BR)="+pbr+"="+(b1*r2)+"/"+((r1+b1)*(r2+b2))

print "P(BB)="+pbb+"="+(b1*b2)+"/"+((r1+b1)*(r2+b2))

Print "Experimental results for "+(n-1)+" trials"

print "P(RR)="+(trr/(n-1))+"="+trr+"/"+(n-1)

print "P(RB)="+(trb/(n-1))+"="+trb+"/"+(n-1)

print "P(BR)="+(tbr/(n-1))+"="+tbr+"/"+(n-1)

print "P(BB)="+(tbb/(n-1))+"="+tbb+"/"+(n-1)

## Wednesday, November 17, 2010

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