Write a program to calculate the probability of two fair dice having sum equal to 7. There are two fair dice and we are interested in seeing whether the sum of the two fair dice having sum equal to 7. Use Monte Carlo Simulation.

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Md Jilani 2019-7-15

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https://ww2.mathworks.cn/matlabcentral/answers/471745-write-a-program-to-calculate-the-probability-of-two-fair-dice-having-sum-equal-to-7-there-are-two-f

编辑： Md Jilani 2019-7-15

采纳的回答： Guillaume

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Guillaume 2019-7-15

You've posted the text of your homework, but haven't actually asked a question.

Hopefully, you're not asking us to do your homework for you (which we won't do).

Md Jilani 2019-7-15

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Sorry sir... This is my first post in this site and that was my fault that I didn't ask any question. Also this is not my homework. This was the question of previous trimester on my school. I tried something on that but I can't get the exact result or I am wrong with my concept. Thats why I didn't post with my tried code. Here it is...

count = 0;
p=1/6;
ntrials = 1000;
sumseven=zeros(ntrials,1);
nAll = 0;
n7   = 0;
prob = 0;
%for probability
for throw1 = 1:6
    for throw2 = 1:6
        nAll = nAll + 1;
        if throw1 + throw2 == 7
            n7 = n7 + 1;
        end
    end
end
%for count
for i=1:ntrials
  throws1  = randi(6, 1);
  throws2  = randi(6, 1);
  sumThrow = throws1 + throws2;   % Do not use "sum" as name of a variable
  if sumThrow == 7
    fprintf('True Sum is 7\n')
    count = count + 1;
  else
    fprintf('false\n')
  end
end
fprintf('Number of throws with sum=7 is %d time\n', count);
prob = ((n7 / nAll)*count)/ntrials;
disp(prob);

I am sorry for my activites anyway...

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Answer 1

Guillaume 2019-7-15

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https://ww2.mathworks.cn/matlabcentral/answers/471745-write-a-program-to-calculate-the-probability-of-two-fair-dice-having-sum-equal-to-7-there-are-two-f#answer_383250

Everything is fine with your code (although the calculation of n7 and nAll could be done with no loop at all), except for your calculation of prob where for some reason you multiply two probabilities together, the theoretical probabilty (n7/nAll) and your monte-carlo probability (count/ntrials), which of course doesn't make much sense.