rand[bias_, n_] := 1 - Unitize@RandomInteger[bias - 1, n]
unbiased[bias_, n_] := DeleteCases[rand[bias, {n, 2}], {a_, a_}][[All, 1]]
count = 1000000;
TableForm[
 Table[{n, Total[rand[n, count]]/count // N,
   Total[#]/Length[#] &@unbiased[n, count] // N}, {n, 3, 6}],
 TableHeadings -> {None, {n, "biased", "unbiased"}}]