percentage statistcal dilema - percentage

Question

Let's say I have 12 values. For this case, let each value be a month in a year. Now write each month on its own separate piece of paper and place that on a table.
So we have 12 pieces of paper in a row along the surface of a table, each with a month of the year written on it.
Each month is assigned a certain percentage to be chosen. For example, January = 15%, February = 9%, December = 5%, etc.
Now, let's randomly pick a number between 1 and 100. We can use two 10-sided die, use a computer random number generator, or whatever you want.
Okay, let's look at the piece of paper that says "January". We now generate a random number between 1 and 100, and it rolls 43. Well, we move onto February now because we were looking for a 15 or lower. Looking at February we generate a new random number between 1 and 100 and roll an 87. Again, we were looking for a 9 or below to choose February, so we move onto March. So on and so forth.... UNTIL we get to July where the random number generated is a 3! Okay, July is picked and we STOP THE WHOLE PROCESS. July is the winner.
My question is: Does each month really have it's percentage value chance of being chosen? Because we stop processing the remaining months if one is picked, I think not. If we were to process each month regardless of one being picked, then yes, each month would have it's face percentage value chance of being picked.
If we must absolutely stop once a month is chosen (which we do have to), how can I make it so that each month has its true percentage chance of being picked?
I think one step in the process is to make sure that each month has a value that if all added together will equal 100, which I have done. But does this really ensure anything?
Code wise (c++), here's what it would look like:
// 15% January
// 9% February
// 9% March
// 8% April
// 8% May
// 8% June
// 8% July
// 8% August
// 8% September
// 8% October
// 6% November
// 5% December
int month = 0;
bool monthFound = false;
if (!monthFound && random(1, 100) <= 15)
{
monthFound = true;
month = 1;
}
if (!monthFound && random(1, 100) <= 9)
{
monthFound = true;
month = 2;
}
if (!monthFound && random(1, 100) <= 9)
{
monthFound = true;
month = 3;
}
if (!monthFound && random(1, 100) <= 8)
{
monthFound = true;
month = 4;
}
if (!monthFound && random(1, 100) <= 8)
{
monthFound = true;
month = 5;
}
if (!monthFound && random(1, 100) <= 8)
{
monthFound = true;
month = 6;
}
if (!monthFound && random(1, 100) <= 8)
{
monthFound = true;
month = 7;
}
if (!monthFound && random(1, 100) <= 8)
{
monthFound = true;
month = 8;
}
if (!monthFound && random(1, 100) <= 8)
{
monthFound = true;
month = 9;
}
if (!monthFound && random(1, 100) <= 8)
{
monthFound = true;
month = 10;
}
if (!monthFound && random(1, 100) <= 6)
{
monthFound = true;
month = 11;
}
if (!monthFound && random(1, 100) <= 5)
{
monthFound = true;
month = 12;
}
if (month)
printf("The month that was picked is: %d", month);
else
printf("No month was picked.");
Here's another way too:
int monthNum = 0;
std::vector<int> chance_;
std::vector<int> month_;
month_.push_back(1); chance_.push_back(15);
month_.push_back(2); chance_.push_back(9);
month_.push_back(3); chance_.push_back(9);
month_.push_back(4); chance_.push_back(8);
month_.push_back(5); chance_.push_back(8);
month_.push_back(6); chance_.push_back(8);
month_.push_back(7); chance_.push_back(8);
month_.push_back(8); chance_.push_back(8);
month_.push_back(9); chance_.push_back(8);
month_.push_back(10); chance_.push_back(8);
month_.push_back(11); chance_.push_back(6);
month_.push_back(12); chance_.push_back(5);
for (std::vector<std::string>::size_type z = 0; z < month_.size(); z++)
{
// Check the chance of the month being picked.
if (RANDOM(1, 100) <= chance_[z])
{
monthNum = month_[z];
break;
}
}
if (monthNum)
printf("The month that was picked is: %d", monthNum);
else
printf("No month was picked.");

Answer 1

You haven't tagged C++, and I use python, so this is Kris's suggestion as python:
import random
number = random.randint(1,100)
if number >= 95:
print ('December')
elif number >= 89:
print ('November')
elif number >= 81:
print ('October')
elif number >= 73:
print ('September')
elif number >= 65:
print ('August')
elif number >= 57:
print ('July')
elif number >= 49:
print ('June')
elif number >= 41:
print ('May')
elif number >= 33:
print ('April')
elif number >= 27:
print ('March')
elif number >= 16:
print ('Febuary')
elif number >= 1:
print ('January')