#include <bits/stdc++.h>
#define ll long long int
#define ld long double
using namespace std;

void mainSolve()
{
    int n;
    cin >> n;
    vector<ld> v(n);
    for (int i = 0; i < n; i++)
        cin >> v[i];
    sort(v.begin(), v.end());
    ld sum = 0.0;
    ld ans = 0.0;
    ld cur = 0.0;
    for (int i = 0; i < n; i++)
        sum += v[i];
    for (int i = 0; i < n; i++)
    {
        cur += v[i];
        ans = max(ans, (cur / (i + 1) + sum - cur) / (n - i));
    }
    cout << fixed << setprecision(10) << ans << endl;
}

int main()
{
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int t;
    cin >> t;
    while (t--)
    {
        mainSolve();
    }
    return 0;
}