Pure Programmer
Blue Matrix


Cluster Map

Project: Central Limit Theorem

The [[Central_limit_theorem#Classical_CLT|Central Limit Theorem]] states that if we take random samples of size N from any distribution of independent random variables, that the distribution of sample averages (`bar X`) should fall in a normal distribution regardless of the type of distribution of the samples. For example our typical random number generators use a uniform, not normal, distribution. But if we take samples of size N, average them, then we should get a sample distribution that is normal with a mean that is the same as our sample source distribution mean and a standard deviation that is equal to the standard deviation of our sample source distribution divided by `sqrt(N)`.

Write a program that accepts a sample size N on the command line and the number of samples to collect M. Then generate the mean (`bar X`) of a sample of size N from random float values [0, 20). Do this M times maintaining a running count of the occurances in an array of 20 by using `lfloor bar X rfloor` (use floor() or int() function) to select the array element to increment. Output a tab-delimited table with the array index in column 1 and the count in column 2. This output can easily be piped into the Histogram project to get a simple graph that should look like a normal distribution centered on 10.0. Notice how as the sample size increases, the standard deviation shrinks?

Output
$ node CentralLimitTheorem.js 3 1000 0 0 1 6 2 8 3 20 4 28 5 60 6 74 7 94 8 98 9 113 10 95 11 101 12 106 13 80 14 43 15 39 16 21 17 12 18 2 19 0 $ node CentralLimitTheorem.js 5 1000 0 0 1 0 2 3 3 8 4 12 5 46 6 74 7 98 8 127 9 139 10 150 11 131 12 99 13 59 14 42 15 8 16 3 17 1 18 0 19 0 $ node CentralLimitTheorem.js 10 1000 0 0 1 0 2 0 3 0 4 1 5 13 6 25 7 92 8 138 9 229 10 202 11 160 12 90 13 40 14 6 15 3 16 1 17 0 18 0 19 0 $ node CentralLimitTheorem.js 25 1000 0 0 1 0 2 0 3 0 4 0 5 1 6 6 7 31 8 157 9 293 10 315 11 158 12 34 13 5 14 0 15 0 16 0 17 0 18 0 19 0

Solution