#include <iostream>
#include <iomanip>
#include <algorithm>

using namespace std;

void run() {
    int aSize;
    cin >> aSize;
    long long int a[aSize];
    
    long long int sumAll = 0;
    for(int i=0; i<aSize; i++) {
        cin >> a[i];
        sumAll += a[i];
    }
    
    int lwl = 0, rwl = aSize >> 1, lwr = rwl - 1, rwr = aSize - 1;
    
    int lSize = lwr - lwl + 1, rSize = rwr - rwl + 1;
    //cout << "LSize " << lSize << " " << " lwr " << lwr << " lwl " << lwl << endl;
    //cout << "RSize " << rSize << " " << " rwr " << rwr << " rwl " << rwl << endl;
    long long int ra[rSize + 1];
    double raa[rSize], rMax = 0.0, rMaxI;
    ra[0] = 0;
    for(int i=1; i <= rSize ; i++) {
        ra[i] = ra[i-1] + a[rwl + i - 1];
        raa[i - 1] = (double) ra[i] / i;
        
        if(raa[i-1] > rMax) {
            rMax = raa[i - 1];
            rMaxI = rwl + i - 1;
        }
        
        //cout << setprecision(21) << raa[i - 1] << " ";
    }
    
    //cout << endl;
    
    long long int la[lSize + 1];
    double laa[lSize], lMax = 0.0, lMaxI = 1;
    la[0] = 0;
    for(int i=1; i <= lSize ; i++) {
        la[i] = la[i-1] + a[lwr - i + 1];
        laa[i - 1] = (double) la[i] / i;
        if(laa[i-1] > lMax) {
            lMax = laa[i - 1];
            lMaxI = lwr - i + 1;
        }
        // cout << setprecision(21) << laa[i - 1] << " ";
    }
    //cout << endl;
    
    // cout << "RMaxI " << rMaxI << " LMaxI " << lMaxI << endl;
    // cout << "rMax = " << setprecision(21) << rMax << " lMax = " << setprecision(21) << lMax << " Sum = " << setprecision(21) << ((rMax + lMax) / (2)) << endl;
    
    // cout << setprecision(21) << avg << endl;
    cout << setprecision(18) << ((rMax + lMax) / 2.0) << endl;
}

int main()
{
    int k;
    cin >> k;
    for(int i=0; i<k; i++) run();
    return 0;
}