//ALL IN
//#pragma GCC optimize("Ofast")
//#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4.1,sse4.2,avx,avx2,popcnt,tune=native")
#include<bits/stdc++.h>
using namespace std;
using ll=long long;
#define int long long
#define double long double
const int N=3e5+7;
const int mod=1e9+7;
const int inf=4e18;
mt19937 rnd(time(0));
clock_t start,final;// start=clock(); last=(final-start)*1.0/1000
inline int read(){int x=0,f=1;char ch=getchar();while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}while(ch>='0'&&ch<='9'){x=x*10+ch-'0',ch=getchar();}return x*f;}
inline void write(int x){if(x<0)putchar('-'),x=-x;if(x>9)write(x/10);putchar(x%10+'0');return;}
double a[N];
double sum[N];
void solve(){
    int n,m=1e10,index=0;
    
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
        sum[i]=sum[i-1]+a[i];
        if(m>a[i]){
            m=a[i];
            index=i;
        }
    }

    double ave=1.0*sum[n]/n;
    ave=max(ave,(a[index-1]+a[index]+a[index+1])/3);
    ave=max(ave,(sum[n]-sum[index-2])/(n-index+2));
    ave=max(ave,(sum[index+1]-sum[0])/(index+1));
    cout<<fixed<<setprecision(10)<<ave<<"\n";
}

signed main(){
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
    int _=1;
    cin>>_;
    while(_--)solve();
}