How do I check if proportion of values in list are mostly positive?

Question

I'd like to return a a boolean variable that tells me whether numbers in a list are mostly positive. For example:

a = {3,2,3,4,-1,-2,-5,3} 

There are 5 positive values and 3 negative ones in list a. That is, 5/8 of the values (more than 50% of them) are positive. How do I get a boolean variable that tells me if this is true or not.

Answer 1

My favorite way, out of many possibilities:

Majority @@ Positive[{3, 2, 3, 4, -1, -2, -5, 3}]
   True

Majority @@ Positive[{-100, -200, -300, 10, 1000000}]
   False

(Change Positive[] to NonNegative[] if wanted.)

Answer 2

Here is one way:

mp[l_] := Total[Sign[l]] > 0

mp[a]
(* True *)

mp[{0, 0, 0}]
(* False *)

mp[{-100, -200, -300, 10, 1000000}]
(* False *)

As written, mp uses a strictly positive test. If desired, we can relax that by changing the test from ... > 0 to ... >= 0 in which case zeroes and equal counts of positives and negatives will be treated as "mostly positive".