#include <bits/stdc++.h>

typedef long long s64;

const int N = 300100;

const double eps = 1e-11;
const s64 inf = 1e18;

int n;

int a[N];
double pre[N];

int p;

bool check(double mid) {
    for (int i = 1; i <= n; i ++)
        pre[i] = pre[i - 1] + a[i] - mid;

    double maxx = -inf, minn = inf;
    for (int i = 1; i < p; i ++)
        minn = std::min(minn, pre[i - 1]);

    for (int i = p + 1; i <= n; i ++)
        maxx = std::max(maxx, pre[i]);

    if (maxx - minn > 0)
        return 1;
    else
        return 0;
}

void work() {
    scanf("%d", &n);

    for (int i = 1; i <= n; i ++)
        scanf("%d", &a[i]);

    for (int i = 2; i < n; i ++)
        if (a[i - 1] > a[i] && a[i] < a[i + 1]) {
            p = i;
            break;
        }

    double l = 1, r = 1e9;
    for (int T = 100; T; T --) {
        double mid = (l + r) / 2;
        if (check(mid)) l = mid; else r = mid;
    }

    printf("%.9lf\n", l);
}

int main() {
    int T;
    scanf("%d", &T);

    while (T --)
        work();
    
    return 0;
}