#include <bits/stdc++.h>
using namespace std;
#ifndef ONLINE_JUDGE    
#define debug(x) cerr<<#x<<" "; _print(x); cerr<<nline;
#else
#define debug(x);  
#endif 
#define ll long long 
 
 
/*
------------------------Input Checker----------------------------------
*/
 
long long readInt(long long l,long long r,char endd){
    long long x=0;
    int cnt=0;
    int fi=-1;
    bool is_neg=false;
    while(true){
        char g=getchar();
        if(g=='-'){  
            assert(fi==-1);
            is_neg=true;
            continue;
        }
        if('0'<=g && g<='9'){
            x*=10;
            x+=g-'0';
            if(cnt==0){
                fi=g-'0';
            }
            cnt++;
            assert(fi!=0 || cnt==1);
            assert(fi!=0 || is_neg==false);
 
            assert(!(cnt>19 || ( cnt==19 && fi>1) ));
        } else if(g==endd){
            if(is_neg){
                x= -x;
            }
 
            if(!(l <= x && x <= r))
            {
                cerr << l << ' ' << r << ' ' << x << '\n';
                assert(1 == 0);
            }
 
            return x;
        } else {
            assert(false);
        }
    }
}
string readString(int l,int r,char endd){
    string ret="";
    int cnt=0;
    while(true){
        char g=getchar();
        assert(g!=-1);
        if(g==endd){
            break;
        }
        cnt++;
        ret+=g;
    }
    assert(l<=cnt && cnt<=r);
    return ret;
}
long long readIntSp(long long l,long long r){
    return readInt(l,r,' ');
}
long long readIntLn(long long l,long long r){
    return readInt(l,r,'\n');
}
string readStringLn(int l,int r){
    return readString(l,r,'\n');
}
string readStringSp(int l,int r){
    return readString(l,r,' ');
}
 
 
/*
------------------------Main code starts here----------------------------------
*/
ll MAX=100000;
vector<ll> readv(ll n){
    vector<ll> a;
    ll x;
    for(ll i=1;i<n;i++){
        x=readIntSp(1,1e9);
        a.push_back(x);
    }
    x=readIntLn(1,1e6);
    a.push_back(x);
    return a;  
}
ll sum_t=0;  
void solve(){
    ll n=readIntLn(2,1e5);
    sum_t+=n;  
    vector<ll> a=readv(n);      
    sort(a.begin(),a.end());  
    ll sum=0;
    for(auto it:a){    
        sum+=it;
    }
    double ans=1.0*sum/n;
    ll lft=0;
    for(ll i=0;i<n;i++){
        lft+=a[i]; sum-=a[i];
        double now=1.0*lft/(i+1);
        ans=max(ans,(now+sum)/(n-i));
    }
    cout<<ans<<"\n"; 
    return;
}
int main(){
    ios_base::sync_with_stdio(false);                         
    cin.tie(NULL);                              
    #ifndef ONLINE_JUDGE                 
    freopen("input.txt", "r", stdin);                                              
    freopen("output.txt", "w", stdout);  
    freopen("error.txt", "w", stderr);                          
    #endif         
    ll test_cases=readIntLn(1,1e3); 
    cout<<fixed<<setprecision(10);
    while(test_cases--){
        solve();
    }
    assert(getchar()==-1);
    assert(sum_t<=(3e5)); 
    return 0;
}