1 #include<cstdio>
2
3 #include<cstdlib>
4
5 #include<cmath>
6
7 #include<cstring>
8
9 #include<algorithm>
10
11 #include<iostream>
12
13 #include<vector>
14
15 #include<map>
16
17 #include<set>
18
19 #include<queue>
20
21 #include<string>
22
23 #define inf 1000000000
24
25 #define maxn 100000
26
27 #define maxm 500+100
28
29 #define eps 1e-10
30
31 #define ll long long
32
33 #define pa pair<int,int>
34
35 #define for0(i,n) for(int i=0;i<=(n);i++)
36
37 #define for1(i,n) for(int i=1;i<=(n);i++)
38
39 #define for2(i,x,y) for(int i=(x);i<=(y);i++)
40
41 #define for3(i,x,y) for(int i=(x);i>=(y);i--)
42
43 #define mod 1000000007
44
45 using namespace std;
46
47 inline int read()
48
49 {
50
51 int x=0,f=1;char ch=getchar();
52
53 while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
54
55 while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}
56
57 return x*f;
58
59 }
60 ll c[100][100];
61
62 int main()
63
64 {
65
66 freopen("input.txt","r",stdin);
67
68 freopen("output.txt","w",stdout);
69 for1(i,50)
70 {
71 c[i][0]=c[i][i]=1;
72 for1(j,i-1)c[i][j]=c[i-1][j]+c[i-1][j-1];
73 }
74
75 int cs=read();
76 while(cs--)
77 {
78 int n=read();ll a[100];
79 for1(i,n)a[i]=read();
80 sort(a+1,a+n+1);
81 double t=0,ans=a[n-1];
82 for1(i,n)if(i!=n-1)t+=a[i];
83 t/=(double)(n-1);
84 for1(i,n-1)ans+=c[n-1][i]*((double)i*t+a[n-1]);
85 printf("%.6f\n",ans/((ll)1<<(n-1)));
86 }
87
88 return 0;
89
90 }
