JSFiddle - React, Tailwind, and code Playground

HTML

<div id="out"></div>

JavaScript

var nums = [];
    for(var i = 0 ; i < 10000; i++) {
        var outOfBoundsChance = .2;
        var num = 0;
        if (Math.random() <= outOfBoundsChance) {
            num = getRandomInt(1, 100);
        } else {
            num = getRandomInt(40, 60);
        }
        nums.push(num);
    }
    
    function getRandomInt(min, max) {
        return Math.floor(Math.random() * (max - min + 1)) + min;
    }

$("#out").html(nums.reduce(function(p,c){ return p + ((c > 60) || (c < 40) ? 1 : 0); },0)/nums.length);