Choose random between two option.

Hi, i want to choose randomly between the "boy" or "girl", how can i do that? Each has the same probability of 50%.

i want to calculate this question:

In a country in which people only want boys … … every family continues to have children until they have a boy. If they have a girl, they have another child. If they have a boy, they stop. What is the proportion of boys to girls in the country? Tnx

Answer 1

[Image Analyst]

Hint:

sexes = {'Boy', 'Girl'};
r = randi([1, 2], 1) % Get a 1 or 2 randomly.
thisSex = sexes(r)  % Extract the sex for this random number.

[Valerie Reinisch]

Hi, what is the solution if the probability for the boy is 60% and for girl 40%?

[Walter Roberson]

r = rand() > 0.60
thisSex = sexes{r+1}

By the way: my modeling says 2/3 girls on average.

[Valerie Reinisch]

Tried it in the meanwhile with this:

r = binornd(1,0.6)

But thanks a lot for this quick answer! (:

Answer 2

[Roger Stafford]

There should be no need to go through such a simulation. For each birth the probability that a boy is born is one-half regardless of all the tricks the family may play.

However if you are addicted to more complicated computations, the average number of boys per family is:

1/2*1 + 1/4*1 + 1/8*1 + ... = 1

and the average number of girls per family is:

1/2*0 + 1/4*1 + 1/8*2 + 1/16*3 + 1/32*4 + ... = 1

You can use symsum to verify these.

[Walter Roberson]

trials = 1E6;
isboy = rand(trials,53) <= 0.5;
child_number_for_boy = sum(cumprod(~isboy,2),2) + 1;
avg_number_of_girls = mean(child_number_for_boy - 1)

avg_number_of_girls = 0.9988

max_number_of_girls = max(child_number_for_boy) - 1

max_number_of_girls = 20