Measure average execution time of a function. I don't claim any credit, I took http://erlangcentral.org/wiki/index.php/Measuring_Function_Execution_Time and put it in a module for convenience.

perftest.erl

-module(perftest).

-export([test_avg/4]).

test_avg(M, F, A, N) when N > 0 ->
    L = test_loop(M, F, A, N, []),
    Length = length(L),
    Min = lists:min(L),
    Max = lists:max(L),
    Med = lists:nth(round((Length / 2)), lists:sort(L)),
    Avg = round(lists:foldl(fun(X, Sum) -> X + Sum end, 0, L) / Length),
    io:format("Range: ~b - ~b mics~n"
              "Median: ~b mics~n"
              "Average: ~b mics~n",
              [Min, Max, Med, Avg]),
    Med.

test_loop(_M, _F, _A, 0, List) ->
    List;
test_loop(M, F, A, N, List) ->
    {T, _Result} = timer:tc(M, F, A),
    test_loop(M, F, A, N - 1, [T|List]).