The Sum of 12 Uniform Random Variables

In Monte Carlo option pricing, one needs to generate standard normal random variables.
Perhaps the simplest way to do this is to use the sum of 12 uniform variables.
Here are the plots and the probability density functions of the sums of uniform random variables.

The Sum of 1, 2, and 3 Uniform Variables

mc_12u_1.gif

1 0≤x≤1
0 True

mc_12u_2.gif

mc_12u_3.gif

0 x<0
x 0≤x<1
2-x 1≤x≤2
0 True

mc_12u_4.gif

mc_12u_5.gif

0 x<0
mc_12u_6.gif 0≤x<1
mc_12u_7.gif 1≤x<2
mc_12u_8.gif 2≤x≤3
0 True

mc_12u_9.gif

The Sum of 12 Uniform Variables

The first figure shows the plot of a standard normal random variable (red line) and that of the sum of 12 uniform variables (blue line).
The second one shows their difference.

mc_12u_10.gif

0 x<0
mc_12u_11.gif 0≤x<1
mc_12u_12.gif 1≤x<2
mc_12u_13.gif 2≤x<3
mc_12u_14.gif 3≤x<4
mc_12u_15.gif 4≤x<5
mc_12u_16.gif 5≤x<6
mc_12u_17.gif 6≤x<7
mc_12u_18.gif 7≤x<8
mc_12u_19.gif 8≤x<9
mc_12u_20.gif 9≤x<10
mc_12u_21.gif 10≤x<11
mc_12u_22.gif 11≤x≤12
0 True

mc_12u_23.gif

mc_12u_24.gif

Box-Muller

According to the Box-Muller algorithm, the random variable mc_12u_25.gif are normally distributed, where mc_12u_26.gif are uniform random variable.
But Mathematica fails to work out the distribution of mc_12u_27.gif.

mc_12u_28.gif

mc_12u_29.gif

Spikey Created with Wolfram Mathematica 8.0