#include <bits/stdc++.h>
using namespace std; 
typedef long long i64; 

int n; 
int a[300005]; 

void solve(void) {
    cin >> n; 
    double ans = 0; 
    for (int i = 1; i <= n; ++i) cin >> a[i], ans += a[i]; 
    ans /= n; 
    int mn = 2; 
    for (int i = 3; i < n; ++i)
        if (a[i] < a[mn]) mn = i; 
    double s = 0; 
    for (int i = 1; i <= mn + 1; ++i) s += a[i]; 
    ans = max(ans, s / (mn + 1)); 
    s = 0; 
    for (int i = mn - 1; i <= n; ++i) s += a[i]; 
    ans = max(ans, s / (n - mn + 2)); 
    cout << fixed << setprecision(11) << ans << '\n'; 
}

int main(void) {
    ios::sync_with_stdio(0); 
    int T; cin >> T; 
    while (T--) solve(); 
    return 0; 
}