Calculating p-value
Based on Chapter 1 of the Statistical Sleuth, showing that given two lists to be compared, we can calculate all possible groupings given the same combined list of subjects.
How to calculate that?
From Online Stat Book: Permutations:
If you have three colored balls, you can order them in ``n!`` ways. (read n factorial). Ie. four balls = 24 possible sequences.
Factorial (factorial(n) in Julia): 4 = 4 * 3 * 2 * 1
3 soups, 4 dinners, 5 deserts. How many meals? 3 * 4 * 5
Permutations are when you have four colored balls, and choose two randomly, and order matters
The number of possible permutations are: `` " "_n P_r = "n!" / "(n-r)!"`` – number of permutations of n objects taken r at a time
When we don't care about the order, we are looking for combinations
Number of possible combinations ``" "_n C_r = "n!"/"(n -r)!r!"`` – number of combinations of n objects taken r at a time
In Julia
function nocomb(n, r)
factorial(n) / ( factorial(n-r) * factorial(r) )
end
And you generate all combinations with
combinations([1,2,3,4], 2)
which returns an iterable, use collect to return, or iterate (for e in …)
