/*
Undo the destiny.
*/
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <cstring>
#include <cstdio>
#include <cctype>
#include <vector>
#include <cmath>
#include <queue>
using namespace std;
#define ll long long
#define FO(x) {freopen(#x".in","r",stdin);freopen(#x".out","w",stdout);}
#define pii pair<int,int>
#define mp make_pair

char buf[1 << 20], *p1, *p2;
#define getchar() (p1 == p2 && (p2 = (p1 = buf) + fread(buf, 1, 1 << 20, stdin), p1 == p2)?EOF: *p1++)
template <typename T> inline void read(T &t) {
    int v = getchar();T f = 1;t = 0;
    while (!isdigit(v)) {if (v == '-')f = -1;v = getchar();}
    while (isdigit(v)) {t = t * 10 + v - 48;v = getchar();}
    t *= f;
}
template <typename T,typename... Args> inline void read(T &t,Args&... args) {
    read(t);read(args...);
}

const ll mod = 998244353;
const double eps = 1e-10;
const int N = 3e5 + 10;
double a[N];
void solve() {
    int n;cin >> n;
    double ans = 0,lst = 0;
    int pos = 0;
    for (int i = 1;i <= n;++i) {
        cin >> a[i];
        ans += a[i];
        if (lst < a[i]) {
            pos = i-1;
        }
        lst = a[i];
    }
    double val1 = a[pos-1],val2 = a[pos + 1];
    double ans1 = val1 + val2 + a[pos],cnt1 = 3,ans2 = val1 + val2 + a[pos],cnt2 = 3;
    for (int i = 1;i < pos - 1;++i) {
        ans1 += a[i];
        ++cnt1;
    }
    ans1 /= cnt1;
    for (int i = pos + 2;i <= n;++i) {
        ans2 += a[i];
        ++cnt2;
    }
    ans2 /= cnt2;
    ans /= n;
    cout << fixed << setprecision(20) << max(ans,max(ans1,ans2)) << "\n";
}


signed main() {
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    int T;cin >> T;
    while (T--) solve();
    return 0;
}