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If I wanted to create a survey that displays the gender of your future babies with counting the ratio of having a male to female is 1.05 to 1. Assuming that each couple will get one baby only. How can I do that in php?

rand (0,1); will generate a random number (either 1 or 0). which can represent the gender. But, how can the ratio be applied as a probability in getting that number?

I know the ratio is very close, and maybe applying the ratio to my function will not effect the outcome at all. but I am doing this to educate myself so, give me an example of how this can be done.

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    Choose between rand(1, 205). If the value is <= 105, it's a male, > 105 is a female. Commented Mar 14, 2013 at 18:11
  • @MichaelBerkowski nice. but still looking for other ways to find the ratio. please do not put your answer as a comment ^^" Commented Mar 14, 2013 at 18:13
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    Think of it as though you have two boxes. One is slightly larger than the other. You throw a ball up into the air, its likelihood of landing in either box (in a vacuum of course) is related directly to the size of the box. Commented Mar 14, 2013 at 18:13
  • .. Maybe blindfolded pin-the-tail-on-the-donkey is a better analogy than a ball... The idea is that you choose randomly between the sum of all your possible partitions, and simply assign the result to a partition range which you have predetermined. Commented Mar 14, 2013 at 18:16

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as per @Michael Berkowski's comment:

/** * Generate random baby gender adjusted by ratio male to female 1.05:1 * * @return * TRUE if male or FALSE if female */ function is_random_male() { return rand(1, 205) <= 105; } echo is_random_male() ? 'male' : 'female';
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1.05 to 1 is equivalent to:

  • Male % = (1 / 2.05) * 100 % = 48,78.. %
  • Female % = (1.05 / 2.05) * 100 % = 51.22.. %

Now depending on the degree of accuracy needed, you can do the following algorithm:

$rnd = rand(0,100); if ($rnd < 48 ) { //male } else { //female }

If you want even more accuracy:

$rnd = rand(0,10000); if ($rnd < 4878 ) { //male } else { //female }
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