error: Program received signal SIGSEGV, Segmentation fault. (Codeblocks, C++)

今天写的一段代码编译未报错，运行出现错误。

#include<iostream>
#include<math.h>
using namespace std;
void statistics(double a[],int n,double *max,double *min,double *avg,double *stdev);
int main(){
    double x[1000];
    double *Max,*Min,*Avg,*Stdev;
    
    int i=0;
    cin>>x[i];
    while(x[i]!=-9999){
        i++;
        cin>>x[i];
    }
    statistics(x,i,Max,Min,Avg,Stdev);
    cout<<*Max<<" "<<*Min<<" "<<*Avg<<" "<<*Stdev; 

    return 0;
    
} 
void statistics(double a[],int n,double *max,double *min,double *avg,double *stdev){
    int i=0;