#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
using namespace std;

using cat = long long;
using dbl = long double;

int main() {
	cin.sync_with_stdio(0);
	cin.tie(0);
	cout << fixed << setprecision(10);
	int T;
	cin >> T;
	while(T--) {
		int N;
		cin >> N;
		vector<cat> A(N);
		for(int i = 0; i < N; i++) cin >> A[i];
		sort(begin(A), end(A));
		dbl ans_le = 0, ans_gt = 1.1e6;
		while(ans_gt-ans_le > 1e-8) {
			dbl avg = (ans_le + ans_gt) / 2;
			dbl sum_le = 0, sum_gt = 0;
			int n_le = 0, n_gt = 0;
			for(int i = 0; i < N; i++) {
				if(avg+1e-8 < A[i]) sum_gt += A[i], n_gt++;
				else sum_le += A[i], n_le++;
			}
			if((n_le ? sum_le/n_le-avg : 0) + sum_gt-n_gt*avg > 1e-8) ans_le = avg;
			else ans_gt = avg;
		}
		dbl sum_le = 0, sum_gt = 0;
		int n_le = 0, n_gt = N;
		for(int i = 0; i < N; i++) sum_gt += A[i];
		for(int i = 0; i <= N; i++) {
			int n = ((i > 0) ? 1 : 0) + n_gt;
			dbl s = ((i > 0) ? sum_le/n_le : 0) + sum_gt;
			ans_le = max(ans_le, s/n);
			if(i < N) sum_le += A[i], sum_gt -= A[i], n_le++, n_gt--;
		}
		cout << ans_le << "\n";
	}
}